In the last couple of days answers in the mobile (non-responsive) site have started scrolling slightly, by what appears to be 16 pixels. This affects the whole answer box down to the add comment button. When you scroll up a little white gap appears at the bottom, as shown:
It's a small change, but it does make it more difficult to scroll down the page because as you scroll down a page with many answers each answer claims one scroll gesture purely to move by 16 pixels without scrolling the page as a whole.
I'm using Chrome 87 on an Android 8 phone. 3.0 pixel density if that matters.