Universal Control is broken - randomly works and then doesn't

Unlike the many other complaints about Universal Control (UC) I've read, my problem is more random and frustrating.

Most of the time, UC simply doesn't work between my MacBook Air (M1) & my iPad (10th gen). This is identical to everyone else's complaints about UC. I've read many of them and have attempted all of the fixes mentioned, such as rebooting both devices, ensuring they are using my Apple account, and so on down the list.

My problem is different in that, randomly, the cursor does move over to the iPad, but it only works for at most a second. It then disappears, and the active cursor shows up on the MacBook. Rarely (& weirdly), it leaves behind a 'ghost' cursor on the iPad when it stops working.

Any clues? I've tried everything. Thanks in advance.