ARGHH. Help please! Date of import, year 2020?!

Hi,

Due to my new Macbook Pro / Big Sur I had to upgrade RB5 to RB6. Unfortunately I have an issue after I moved my database.

The date of import is not correct. Day and month seem to be fine, but RB shows that all tracks were imported in the year 2020, which is not true. The funny thing is that when I copy tracks to a playlist the correct date of import is shown in that playlist. However the dates of import in My Collection do not change. 

How to repair this issue? Thanks.