on the permissions page (/admin/config/people/permissions) there is a problem once there are more roles than can fit on the display across the top.
the column headings, which are sticky at the top of the list of permissions, work fine when scrolling down/up. but when you have more than a few roles, the headers do not remain at the top of their column when you scroll left/right. this makes it almost impossible to accurately set permissions for roles that don't fit on the display horizontally.
not sure if that would be considered a bug or not, but it sure makes assigning permissions difficult (once you have more than a few roles).
edit for clarity: when the page first loads, if you don't scroll down, the headers scroll horizontally correctly. once you scroll down enough to get the header row to get "sticky", it no longer scrolls horizontally.