Scheduler Card stopped working

I've been using the SchedulerCard plugin for months with no problem. Suddenly the card's layout is corrupted and what changes I can make on the card are not saved. In particular, I cannot change the schedule.

I've got v4.0.16 of SchedulerCard which is not the latest, but I can't update without updating Home Assistant itself (I have 20205.4.2), and I can't upgrade that without new hardware (I have a RPi3 with ARMv7). But it was working, and now it's not, and as far as I know there were no updates or changes.

Any ideas or suggestions?

It is very likely your answer is here somewhere in these quotes. Some problem you see could have well been fixed in newer versions and it just decided to manifest for you.

If you start noticing any other odd things happening, SD cards often fail in unusual ways. How to Troubleshoot Raspberry Pi Crashing