I shoot with a Nikon D850 and a Nikon 600mm f4E FL ED VR AF-S Lens
I sometimes use a 2 x teleconverter (AF-S TC-20E III)
April 2022 I was photographing at a Peregrine site and all was fine.
I put on the teleconverter and took a few shots then removed it.
From that point the 600mm lens would not autofocus.
I checked all settings, removed and re-set lens, removed battery, cards......... I tried everything.
Autofocus worked fine with another lend with and without the teleconverter therefore issue seems to be with the lens.
Next day I tried it again and still no autofocus.
I drove and dropped all the kit to "Advanced Camera Services"
Next day they tried the lens and couldn't;t find any fault with it. It worked fine.
They checked everything and nothing was stuck, dirty or faulty.
I collected it and used it occasionally through the summer with and without the teleconverter. No problems.
27 July I was in a hide photographing birds. No problem.
Woodpecker landed a way off so I put on teleconverter and took some shots.
Teleconverter off and then same thing again. No autofocus.
I tried everything and nothing worked.
I put the 600mm lens on someone else's D750 and it would not autofocus on that either.
I put another lens on my D850 and it auto focussed perfectly. Issue is with the lens.
That evening... still not working
Next morning... Still not working
29 July I tried it just on the off-chance and it was and is now working as normal
Called ACS who said it "may" me an intermittent fault with the DC/DC ???? but they aren't really sure.
31 August I tried it all again with and without the teleconverter and it's working perfectly.
My issue is that I drove 4 hours to get to this hide to photograph birds in flight. 10 minutes into this shoot it stopped working. That was a very expensive wasted trip.
The kit is clean. It has not been bumped.
Any sensible suggestions?