Basecamp 4.8.9 - Backup / Restore removes track timestamps

Hi, 

i want to migrate my basecamp data from BC 4.8.9 running macOS High Sierra to a new mac running catalina and BC same version.

I tried backup on old mac and restore into a fresh library from the backup file, which somehow works.

However all tracks loose their timestamps and elevation info.

Due to elder posts this could be a side effect of a historic bug ...

Is there any recommended procedure to migrate the data?

Thanks
Hajo