I am using Oracle SQL*Plus 18.104.22.168.0.
Whenever the application is opened and I start typing, the cursor takes on a mind of its own and does not stay at the insertion point. Also BACKSPC does not fully delete the characters from the screen and puts the cursor in the wrong place. One has to mentally keep track of where the cursor actually is. Also left & right arrow keys do not work at all.
I am sure this is related to the font used in the application window. When other clients log onto the same server, they do not have the problem and can edit text quite normally. Their default font is different but I cannot see how to change it.