my EOS R locking-metal-button (not sure what u call it) on the lens mount got stuck.

I had never try to unlock it previously, has always had the mount adapter on it.

At first, the release button wasn't 'responding' when I try to dismount it.. after a few tries, it then released. I haven't noticed the lock stays recessed to the mount until I tried changing to another lens - the whole mount adapter turns together with the lens. Anybody else experiencing this problem before?

I guess I have to head to Canon service center and see if they can repair it on the spot.. should be a simple fix, but I would not want to mess with it since it is still under warranty..

Here are some pics..

That is really bizarre. Send it to Canon for warranty repair.
You don't want your lens to fall off because of this. Maybe got some dirt clogged up, or the lubricant inside dried up or something.
Thanks for sharing though, I myself is EOS R user, will take note of this.

I have sent it to Canon this morning... the thing stuck due to moist and dust from my last hiking trip. Looks like a simple fix at first as the technician straight away take a look at the camera... then it seems it would be best to service and clean the whole camera when they find more parts needs to be clean.

On the trip, it was raining part of it and the humidity is quite high, the camera does exposed to rain but indirectly.. more like spills and wet hands. The 1635L lens survived OK, I tried it in these similar conditions many times with 5DMkII... first time doing it to the R as I read the weather sealing is as good as well excepts for the viewfinder area. 2nd day of hike, the camera does jam on me.. as I can't use it on the 2nd and 3rd day.. back from the hike, I let it dry up and it works fine, thus the reason not sending it for servicing... yet..

Well... I guess I would not treat the R the same way as my old camera. Great job for Canon as the check the camera thoroughly.. appreciate these kind of services. Later in the evening I got an sms from Canon that my camera is ready for pickup. Excellent!

thanks for sharing this.
now this is worrying me. I do shoot a lot in heavy rain previously with my 6D and it survived pretty decently. There was only once that I was out shooting continuously in rain for more than 2 hours and it started to to behave weirdly. But left it overnight in room with radiator and it worked fine next the day.

I thought this should be better than my old 6D but now doesn't seem so.

You're welcome. I'll be more aware on handling the R from now in wet and humid conditions.. at least I now know it's limits.

Thanks bro for the update.
Will have to becareful myself too.
Generally DSLRs like 5d series will be more durable compared to mirrorless. EOS R does give me the feeling of not as weather sealed as my 5D3 too.