Error message: Couldn't deserialize value

I kept getting these error messages on startup.

11:07:22.208 [ERROR] [] - Couldn't deserialize value ''. Root cause is: May 5, 2020 10:43:03 AM

I can’t figure out how to solve it. I searched for the string May 5, 2020 10:43:03 AM and found it in one file habot_cards.json

I deleted this file in userdata/jsondb/habot_cards.json but the error messages kept showing up everytime openhab (re)starts.

I noticed that there are also userdata/jsondb/backup/xxxxxhabot_cards.json, and once I deleted userdata/jsondb/backup/habot, the error messages no longer appeared.

It seems weird, as if openhab read the files inside userdata/jsondb/backup/ too.