Backups of subscription can not be created. When trying to create a backup it looks like it was created successfully, but there is no backup in the backup list.
/usr/local/psa/PMM/logs/pmmcli.log contains the following line:
Invalid name in entity [Ln: 229, Col: 463648914]
Plesk Automation unable to backup data if some web hosting settings contains symbols incompatible with XML. The behavior was considered as internal software issue with id #PPA-2391.
In order to fix the issue please install update 11 as described in the article.