When installing a plugin or manually purging caches, completion takes around 40 minutes, causing a gateway timeout. 

It appears that the MUC cache takes most of the time. 

Has anybody else run into this problem and/or have a possible solution?

We are running Moodle 4.1.6 (but the same problem has been happening for ages in previous version), Postgresql 12.17 on 1 RW/2RO nodes and 6 nodes for moodle on Redhat8. 

The moodledata folder is on an NFS drive shared between all nodes.