Mistake markers persisting after changing the number in a field

[ponko2MSL]

I started a 12x12 game last night and partially solved it, then turned off the phone screen and went to sleep. When I turned it back on, I noticed there was a marked mistake with a duplicate 4 in one field.
I erased that field, but the red circles and lines indicating a mistake still remained.
I entered a presumably correct value of 1 in the marked field, but the markers stayed visible.
I cleared the field and used a hint on it (which entered a 1), but the mistake markers remained.
I went to the other interactable circled field containing a 4 and changed its value to a 5. I got a new mistake marker on top of the old one, pointing out the existence of another 5 in that column and row (see second screenshot). I changed the value back to a 4, and the new marker disappeared as it should. The previous markers remained though.

In the end I was able to finish the game without the mistake markers ever going away. (It turned out that the field that i had changed to a 5 in the second screenshot should actually contain a 6, but I don't know if that's relevant to the markers.)

I don't know how or why this happened, as I have used the app extensively before on this device without any problems. (According to the high scores screen, I've played for over 400 hours in total.)

My device is a Sony Xperia 10 III running Android 13 (build number 62.2.A.0.525 release-keys).