iMac accessibility keyboard: minimizing the keyboard takes up most of the screen

I have the same issue that LaughingElefant reported in a separate post (see MacBook Air accessibility Keyboard; minim… - Apple Community), except that his problem occurred on a MacBook Air, whereas mine is happening on an iMac M4. Hitting the minimise button on the Accessibility Keyboard causes it to take on the form of a giant black rectangle with "Keyboard" written in the middle. See the video in LaughingElefant's post. His problem doesn't appear to have been resolved. I didn't have this problem to start with, and I don't know what caused it.