applications – HELP: the backspace key does not work

I use the Android HELP app on Android Oreo 8.1. It's happened a few times now that when using Java code from the Java code sample, the Backspace key did not work (it did not roll back the cursor key and delete characters; instead, the cursor remained where it was and does not move).

I've tried to change the keyboards, this occurs in both GBoard and CodeBoard, so this is not a keyboard problem but a HELP application problem.

Is it a bug or am I missing something? How am I repairing it?