Problems syncing old version 0 libraries

I’m running Seafile Server CE version 6.1.1 and some users have old version 0 libraries. Seafile Clients up to version 6.1.8 can sync these libraries, but new version
7.0.x clients can’t.
Debian gui client 7.0.2 gets stuck in “indexing file”, with no network traffic.
These clients were updated without the user being informed of the
dropped repo version. Is there any documentation describing this behavior?