Shorty answer: mechanical shutter malfunction? Long answer: I had an issue like this on my Nikon D750 about 8 years ago. It occurred in one of about 400 photos. I shot manual with mechanical shutter. That model had issues with the mechanical shutter and many were recalled. Nikon said my serial number was not affected and would not take it back . Finally about 4 years later I got an email that my serial number was recalled. By then it had 99,000 exposures. They took it back, replaced the shutter, cleaned it up so it looked new. It never had the problem again. I gave it away to my daughter at 160,000 exposures and she has not reported it as a problem since she got it.

I have shot Nikon since 1971. The oldest lens I own is a F mount 13.5cm 3.5 Nikkor c.1963. Which I purchased used as my first 135mm. My first 50mm 1.4 was also purchased used - made in 1969. They mount and operate on my Z9. Kinda clunky but works correctly. And on my Z7, Z6, D850, D200, and my F. Most of my AF, AF D and previous lenses will mount and operate manually on the F. Even the old F mount intrusive fisheyes will (mostly) mount and operate properly on the Z camera’s. I’m annoyed that my screw AF lenses don’t autofocus on the Z series with the FTZ. But otherwise they work fine.

During the same time period Canon has had the following lens mounts:

1959 R
1964 FL
1971 FD
1987 EF
2003 EF-S (EF compatible)
2012 EF-M
2018 RF (EF lenses can be adapted for the the R camera’s.).


Note for the ignorant:
R, FL and FD are the same mount.
EFs is so crop lenses are not wasted on FF cameras.
EFM will take EF lenses and work just fine.
RF will take every single EF lens with adapter and work 100% or even better especially with the control ring.

Nikon "Mount" changes using your logic:
Pre AI not all worked with AI and could not be converted.
AI Converted
AI
AI-s
Nikon 1
AF/AF-D
AF-S
AF-I
G
AF-P
Z which does not support but a couple of all the previous lenses including auto focus lenses.

Z orphaned thousands of Nikon owners with un-useable lenses as shown in compatibility charts, and even in the older mounts there was a lot of incompatibility, thus the need for compatibility charts.

100% of EF/EFs lenses are fully compatible with the RF mount with the adapter. (EF lenses have been around for 35 years and anyone under 50 would likely have no clue about FD lenses and could care less) Additionally ALL FD/FL/R/M39 Canon lenses work on the RF mount cameras. So those that still have those great lenses now use them again with the latest R cameras.
See photos, ALL have the same identical mount and I have mounted ALL on R/FL/FD cameras interchangeably.
The last photo has FD/FL/R lenses mounted on all the cameras shown and NOT on FD/FD but so called mixed mounts and as you can see they all mount just fine.
Your ignorance shines through loud and clear.