Issue importing my epub Books

I cannot add my own epub to Books on my Mac. Every time I try I get an error message like "Importation: 0 on 1. Fail(s): 1 " The epub I purchased are OK though. I can add PDFs et audio books with no problem.

I've tried creating a new Mac user, and in that user it work fine. I can import my epubs.

I've tried deleting Library/Containers/com.apple.BKAgentService and starting from a new Books Library. But this doesn't help.

The only solution I am left with for now would be to create a new user and transfer all my settings there. I have a lot to transfer and this will take me a full day.

Would you, guys, have any idea how to solve this?