Canon 5d4 flash question??

[swanseamale47]

I was using a 5d4 yesterday and noticed an odd issue with the flash. Any ideas?
Camera on auto iso, program mode ettl flash. Camera setting f4 1/60 400iso (correct exposure with flash in low light room) Now turn off flash and camera stays on same setting but underexposing in available light. Remove flash off camera and camera sets 1/100 at f5.6 5000 iso (correct exposure without flash.
The camera stays on the flash setting in program mode until the flash removed from camera. I've tried the same thing on a 5d3 and a 6d2, plus a 90d 750d aand a 7d, they all work fine once flash is switched off, and the flash can be left on camera.
I noticed if I turn external flash to disable in the menu the camera works fine.
Now is it a setting I'm missing?, I'm fairly sure my other 5d4 dioesnt do this (dont have it here to check at moment) and none of my other canons do it, or do I have a faulty 5d4???

 

[Phil V]

It sounds like a fault to me.
But I reckon that’s what you think too.
Once flash is switched off the camera settings should revert as you expect.

BTW I’m impressed with your bravery, I never dare let the camera set anything auto when using flash as key. Am I a control freak or a coward?

 

[Gav.]

My 5D IV reverts straight back if flash is switched off.

May be a reset or firmware refresh could fix a glitch. Are the contacts clean and clear of anything that could arc.

I'm a control freak too

 

[swanseamale47]

Contacts look fine. P works fine for quick shots most of the time, I switch between M P and AV (almost never use the other modes) depending on what I'm doing and time. If I'm out on a wander with Tamron 28-300 I tend to leave it in P. Most of the stuff I shoot for myself are abstracts, a light switch, or a bit of building etc, I was in a party when I noticed, switched from a few flash shots to candid and noticed the issue. Think I'll have to get it checked.

 

[Gav.]

Try a firmware before paying for an inspection.

 

[swanseamale47]

Ok, update. I'm now fairly sure it's not the camera. I tried a Yongnuo flash on camera (the new round head godox copy, cant remember the model) and the camera works normally. Turn flash off and bingo back to normal. Swopped them back and fro and it's only doing it with a 580ex, yet that works fine on like 6 other cameras including a 5d3. The camera works fine with my old Metz canon flash too.
So it now looks a like a flash issue, or some sort of compatability problem.
Time to switch to Godox? (mind I haven't tried it with one of thoseyet)