The rock in middle on de_abbey has inaccurate hitboxes for grenades and spots that cannot be shot through with every weapon all around the rock, as seen in this clip:
https://gfycat.com/SpottedEcstaticArcticwolf
The quality isn't exactly sublime, but it should showcase the issue sufficiently.

Another issue is a window in the mid area that you can hide in, similar to the one in earlier testing in ct spawn:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1636452981
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1636453224
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1636453307

There appears to be another small issue with window clipping here, near ct spawn:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1636451937
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1636451882