I get the error shown in the attached screenshot every time I open H15 beta.
Additionally, there are no album cover images shown, but when I open them via "View Original...", the image is loaded in the external image viewer.
Helium 14 shows the cover for all albums correctly.
Please open a support ticket for this.
The issue seems related to your specific database and we might need a backup of your database to test it out in further detail.