Update 21.0.7. to 21.0.9 Create Backup Time-Out

I-m working with Nextcloud under Plesk.
I try to update my nectcloud 21.0.7 to 21.0.9. At “Create backup” it stopps:

*Create backup

Parsing response failed.
Show detailed response

<html>
<head><title>504 Gateway Time-out</title></head>
<body>
<center><h1>504 Gateway Time-out</h1></center>
<hr><center>nginx</center>
</body>
</html>


No idea how I could solve this problem.
Would appreciate any help. Thanks.

Regards,
Thomas

The logfiles might help you to identify the problem:
https://docs.nextcloud.com/server/21/admin_manual/issues/general_troubleshooting.html#id1

and the logfiles of your webserver. Could be anything from timeout, exhausted resources, permissions, …