Cannot change the settings of domain. The error 504 is thrown:
Internal error. 504 Gateway Time-out nginx
plesk-agent executes another task (most probably backup or migration) on the service node and does not respond the PA requests to change the hosting settings.
plesk-agent runs in single-thread mode can process only one request at the same time. Other requests will not be responded.
The behavior is caused by software issue #PPA-2138. The fix is included in MU #10.
Update PA to the latest version: