Windows move to different monitor when multiple monitors turned off and back on

Ubuntu 19.10, gdm3 3.34.1-1ubuntu1, cinnamon 4.0.10-2, cinnamon-screensaver 4.0.3-1, nvidia-driver 435.21-0ubuntu2.

I have a TV set connected to my computer as a second monitor (for displaying YouTube videos, etc.).

When I turn off both my main monitor and the TV for the night, and turn them back on in the morning, I often find that the windows I had left open on the main monitor (email, browser, xterm, etc.) have moved from the main monitor to the TV and need to be moved back individually to the main monitor (via the "move to the other monitor" function on the taskbar icons).

This doesn't always happen -- sometimes the windows show up on the main monitor where I left them the night before, and sometimes not. Maybe 50-50, one way or the other.

The main monitor is configured (in the Display settings) as the primary monitor, and the taskbar panel remains on the main monitor -- and when I wake up the screen saver to unlock it, the password dialogue always shows up on the main monitor -- but the windows may end up on either device after I've unlocked.

It doesn't appear to make any difference what order I turn the monitor and the TV off/on. In particular, I've conscientiously turned off the TV before locking the screen and turning off the monitor, and then turned on the monitor and unlocked the screen before turning the TV back on, but the windows frequently still end up on the TV instead of the main monitor.

I would like to somehow flag the windows so that they will stay put on my main monitor when I turn things off at night and turn them back on in the morning -- or, even better, I would like the windows to remain associated with the same device and not move around on their own.