I bought an R8 from B&H and used it mostly with heavier lens (RF24-105L, EF70-300 with nano USM + adapter). I used it in the same way as my RP and 6DII. Within a month, the grip got "loose", in the sense that if I hold the grip tight and tried to squeeze/move the grip, I could feel that the grip moved a little bit and it made some clicking/cracking noise. The noise/move seemed to come from where the grip part meets the top panel right around the shutter.

I did an exchange and also bought the extension grip hoping that it would make the grip structure stronger. I also then handled the R8 with more care, like not picking up the camera with my index finger right under the shutter. However, after a little more than a month, the grip is a little loose again, but this time it's just a little bit and doesn't bother me much (so far).

My RP's grip also gets a little loose after about one year's usage, but I can mostly fix the problem by adjusting the three screws (two on the side, one on the top panel). I can't achieve the same with my R8.

So at this point my personal conclusion is that the R8 build quality is not as good as I would like to have and even a little worse than RP.

What's your experience with your R8?