I’m not sure exactly when this started occuring but it may have been with a recent update to Android 11. I’m on a Pixel 3a XL. The issue is that if I highlight from somewhere above the final line in the text and try to drag the selection down into the last line, it will not go into the last line. This happens in sentence mode (if the sentence is multiple lines) and normal mode.
I can highlight want I want by starting the highlight on the last line and dragging up. However, it’s not ideal.
I think it started around the last 2-3 weeks which may correspond to the update to Android 11, but not sure. I don’t have the issue on my android tablet.