I have seen this too. Tap on the new line and the cursor moves, then all is well.
It has been discussed before and appears to be a problem with GBoard. I switched keyboard for a while because of it but finally decided to live with it since GBoard is my preferred Android keyboard for everything else.
When using Chrome on Android, if some text is typed in the editor, and then enter is pressed, the cursor doesn't move to the line below like it should, it stays in place. This is after pressing enter: