Cards are sporadically reset to Learn/New

In decks with multi card notes (2-4 cards per note), I’m facing the issue that some of my cards that I’ve already studied are seemingly randomly reset to the new status.

For example, I studied the card sauber → clean (De-En) on February 23, had review on February 25, but now it is shown as “New #308” in the card browser:

Also, this card also has “Target R” as “N/A”:

I have cards with the following history:

I don’t understand why they are repeatedly reset and how that could happen. I’ve heard that it might be because of the synchronization issues but I always try to sync the phone and the PC before switching between them and I never repeat my cards using the desktop Anki.

I use the computer version of Anki (24.11) only for cards creation and I study them using AnkiDroid (2.20.1), I use the FSRS scheduler in my decks. I also have the options “Bury new siblings” and “Bury review siblings” in decks enabled. I don’t use any addons except for “FRSR Helper” which I’ve used several times to balance the sibling cards. I initially thought that it might be because of it, but I’m getting cards reset on days when I didn’t use that addon.

There are several inconsistencies there – rep count 0, due date missing, memory state missing, “Last Review” date, but is still New. All of that together looks just like a sync issue would look.

The question is – do you sync when you open the app AND when you close/leave the app, on every device, every time? If you’ve got cards with review history on AnkiDroid and edits on desktop at the same time, they can definitely end up in an inconsistent state like this. Add-ons that make changes “on sync”/“after sync” can aggravate the problem – and the FSRS Helper is not immune, if you use that functionality. Happily, that add-on can also be the cure.

See the what-to-do-now steps at the end of: Scheduling differences between Anki desktop and Android - #4 by Danika_Dakika