billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Sounds like all of the contacts on the lens are not making contact with all of the contacts on the camera body. If you have to twist the lens to get the original setting back sounds like the lens is not seating properly on the camera, and the lens has not moved far enough to the right to make contact with all of the contacts on the body.
This does not sound right, if the lens is clicking in place and you still have to twist the lens to the right to make contact something is wrong with the lens.
You should do two things,
1. contact Sigma about the problem and seek their advice about resolving it.
2. Next time, buy a lens that is specifically designed to work with your D500, like the NIKON 200-500 5.6 lens. Then your problems will be over.
Good luck and keep on shooting until the end.

Brucej67 Loc: Cary, NC

No one has asked does he have a problem with any other lens on the camera (to make sure it is not a problem with the camera mount). I have this Sigma lens as well as other Sigma lenses and it is a great lens, not all Nikon lenses are top quality either, I had the Nikon 200-400mm F4 VRII with a burned out focusing motor. All lenses can have problems, but one thing I like about the way Sigma and Tamron make their quality lenses is that you can fine tune auto focus at any focal range covering the entire spread of the lens right on the lens instead of one focal length in the camera.

Hunter Lou 1947 Loc: Minnesota

I too have the Sigma 150-600 Sport. I experienced a loose lens on my 7D Mark II. I called Sigma and they suggested I send in both camera and lens. I did and they say they adjusted the lens but I still notice some movement. It does not seem to affect my shooting. It just cost me the shipping and insurance cost to send it to them. They did not charge me for adjustment or sending back to me. They were very fast on their repair turn around. Stay Safe and Wear Your Masks.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

HE HAS STATED THAT HE HAS NO PROBLEMS WITH HIS OTHER LENSES. PLEASE RE READ HIS POST.

Brucej67 Loc: Cary, NC

Sorry, there is no need to shout, just trying to be helpful.

Thomas902 Loc: Washington DC

Fred Frank did your Sigma optic ever work correctly?
When did you first notice the issue?
What had changed prior to the issue appearing?
Has the Sigma suffered any impact damage?
Has the D500 suffered any impact damage?
Was there a major change in weather conditions that may have played a part i.e. excessively high humidity?
Did you purchase the Sigma "new" with a Sigma Warranty? or was it a "previously owned" lens
Did you purchase the Nikon D500 "new" with a Nikon full warranty? or was it gray market or a "previously owned" camera?
Have you contacted Nikon Support on this issue?
Have you contacted Sigma Support on this issue?

Sorry for the interrogation Fred Frank...
However if you came to the ER with an issue you would be subjected to the same rigorous interrogation by the physician in responsible charge...

My best friend is currently on the front line of the covid19 pandemic... She's an ICU Nurse (the top gun of the nursing profession), albeit a nurse anesthesiologist might challenge this inference. She has to document virtually everything that is happening with her critical care patients BEFORE she can leave the hospital after her 12 hour shift..

Kudo's to Hunter Lou 1947 post... He's totally on point here...
Fred Frank I shoot commercially and have an identical copy of each camera body and lens I use on assignments. They always come with me to every paid gig I'm on. They are also priceless in troubleshooting issues such as yours Fred.

btw I shoot Nikon FX glass exclusively.... However I rely on Sigma glass on my DX bodies. Why? Because Nikon refuses to make "Pro Grade" DX glass... Sigma has filled that gap in spades...

All the best with your lens/camera combo Frank...
I'm certain either Sigma or Nikon Support can be of service to you...

Stay Safe and Wear Your Masks.

Brucej67 Loc: Cary, NC

I like your approach to his problem, very intelligent, my hat is off to you.

User ID

ROTFLMFAO

You own 40 pieces of Nikon and are not familiar with the zero f/stop readout .....
and have NO idea who you’re talking to. And neither am I obliged to prove anything about myself to YOU.

If you were to disagree with me that the sky is blue, I would not be obliged to prove to you that I know it’s blue because I’m NASA physicist. I’d just leave you blathering that the sky isn’t blue if we haven’t asked it enough questions yet.

No I’m not with NASA. Neither do I see evidence of your claimed credentials given your lack of common experiential knowledge. Me a troll ? Well on occasion I will troll a stuffedshirt!

Try reading the post following this one, by olemikey. Perfectly common sense. No claim of a professional resume, cuz none needed. No stuffedshirt there.

olemikey Loc: 6 mile creek, Spacecoast Florida

Big long heavy lens on a little camera - Yes possible dirty connections, worse, a loose mount, more likely the lens, but could be camera. If you are holding the lens at any time just via the camera body, you are putting over 6 lbs of stress on the mounts - if everything isn't tick tight and locked in you might lose the connection. When using hand held you may be putting even more stress without realizing.

Question(2-part) - Does this happen when both are properly supported? Does it happen hand held, or when on tripod, or both? Things to check: The screws on the lens mount, and the screws on the camera body (make sure you have a properly sized screwdriver, don't want to make things worse). The fit/lock should be tight, should not flex or partially rotate, if not tight something is askew. If that (mount screws) are all OK, then clean the contacts (carefully) on both the camera body and the lens and see if any change. If you cannot nail it down ask a shop for their opinion, or send in wnen you can. Other method would be to change handling habits for less stress. My $.02

Fred Frank Loc: Roanoke Alabama

Thanks everyone. I'm in the process of contacting Sigma. The camera is not an issue. My Nikkor 70-200 works as it should. Y'all have shared vast knowledge about the issue and its greatly appreciated. I'll give feedback as I receive more solid diagnosis

Brucej67 Loc: Cary, NC

Sorry you feel that way, I have nothing to prove to you, every one can learn, (stuffedshirt), no just an average Joe, not rich. If you are a Photo Master I salute you, but I feel you are another hateful troll and wish you good day.

olemikey Loc: 6 mile creek, Spacecoast Florida

Good luck with the effort. I have had this happen to me with a couple of big ole heavy lenses, (as I shoot a lot of telephoto), often hand-held (pre-plastic - heavy metal lenses) and even on a couple of the big ole metal/plastic jobs. In one case it was the teleconverter I was using that contributed to electrical signal loss, another was due to tight, but not tight to spec lens mount screws....yet another time it turned out to be a connection problem with the lens mount contact pins/housing - it was loose. Another pairing, smaller but heavy zoom, intermittent action was long time between, never really figured that one out, but still use all the gear I've mentioned. Thing is, with the mounts and connectors they can often look alright, but with tension/weight on them things can change. Anyway, could luck in your quest.

islandboy4147 Loc: Savannah, GA

If this applies to your issue, try this out.
I own this lens and had the same problem. On the end where it attaches to the camera you will see 6 small Phillips head screws. With a Jewelers screwdriver, gently tighten each in a diagonal pattern finger tight. Then go back around and snug all 6 again. Be gentle and do not over tighten.

Hunter Lou 1947 Loc: Minnesota

I'm reluctant to mess around with anything I don't have knowledge of. So It's best I leave it alone, thanks anyway.

olemikey Loc: 6 mile creek, Spacecoast Florida

Good safe process, try it if you can get the right screwdriver!!! I wish I knew the approx. micro torque values, but don't.