Cbt for image backups not working anymore?

When i normally check the backup protocol, i see an entry ‘Change block tracking active’.

But yesterday:

The corresponding line has gone.
Does that mean cbt is not working anymore?

Server: 2.1.19 on a QNAP TS-453Pro
Client: 2.1.17-cbt on a Windows 10 Pro

What can i do?

This could have been caused by the update to 2.1.17. In this case it will work again with the next image backup.

ok, i’ll see.