What causes several Backoffice Long Operation items, which seems to be causing performance issues?

Hybris: 1905.14

I'm having performance issues on a Hybris instance hosted in CCV2. It is slowing down the storefront and the backoffice. If I go to HAC > Monitoring > Suspend, I see several Backoffice Long Operation items. The thread dump also show several threads related to backoffice.

There are no cronjobs running and the Triggers have been set to active=false. After some time, the server needs to be restarted, since the backoffice no longer loads. Lastly, the server cannot be initialized, since it contains data.

There is minimal configuration in backoffice, just some XML configuration to customize the treeview of different usergroups.

I am not able to replicate the performance issue on my local. Any ideas what may be causing these Backoffice Long Operation items?