I guess I'll have to post some of the photos when (and if) I return ;-)

LOL!

I'll be spending time in Alaska's Kenai Peninsula this summer photographing brown bears during the salmon run. I plan to take to take two camera bodies with lenses and CPLs already attached (Fuji X-T2 w/18-135 & Canon 80D w/Sigma 150-600). The environmental conditions will not be conducive to changing lenses or putting a bag or backpack down to swap cameras or access other gear since it's very wet in most areas. So, I'm looking for a bag or backpack that will give me the ability to store and swap the two cameras without setting it down while hiking and shooting. Suggestions?

The Fuji X-T2 with 18-135 lens. It has all the mechanical controls a camera can offer, is the smallest body that is still easily manipulated by my hands, and the lens is reasonably sized while producing very sharp images (even in low light) and covers the focal length range most of us use for the great majority of our photos.

Yes, and UHH!

I called Apple and just finished reinstalling OS 10.13.3. Well, THAT WORKED!!!!! At least, so far. I say that only because back in January when all this started, the symptoms ramped up gradually over time. So, my confidence is at something less than 100% right now. Of course, I will post again when enough time has gone by without incident. I also have to reinstall the OS on my MacBook Pro, but that should yield the same results.

Thanks to all of you for your help! I feel like a free man again ;-)

OK, will do. I'll report back when it's done.

OK, OK, I'll do it. Thanks for the prod. Can you suggest somewhere online that lists the procedure?

Apple original.

If I do that will the EXIF data move to the new library with the photos? That would give me the date each photo was taken and make it easier to put it in the right album.

Yes, five weeks of waiting with no answer has been torturous. So, I just fired off an e-mail to the Apple tech asking about reinstalling the OS. I hope to hear from him soon. Thanks for your interest.

Thanks for the suggestion to reinstall the entire OS. The problem began before I upgraded to 10.13.3, so the tech didn't think a reinstall was necessary. It couldn't hurt, though, and I'm getting desperate now. Also, I'm not sure where you got the impression that the issue has been around for five months. I first had the problem in early January and reported it soon after. So, it has now been about five weeks. Sorry if I wasn't clear about that in an earlier post.

Time to answer a few of your questions:
1) I'm using 10.13.3 on both computers.
2) I bought both computer new from Apple. The iMac about 2-3 years ago and the MacBook Pro about six months ago when the latest version came out with the screen that replaces the function keys.
3) Yes, I've been using Time Machine since it was first released.

I'd like to add that the Apple tech said my photo library is not at risk. Plus, I'm fully backed up via Time Machine and iCloud. He also said he relatively confident that the problem lies deep within some obscure non-photo file. I'm just pray that someone has had a similar issue and knows how to fix it.