We ran into this as well after upgrading to 2111 for Log4J compliance back in December. It took a few weeks for the issue to become apparent as we have a multi-tenant environment with mixed Horizon Client versions.
Any endpoint running Horizon Client 5.x or older was impacted with the 8.4 agent. If we created a special pool running 8.1 agents, the issue no longer occurred. There wasn't a specific response from VMware other than running Horizon Clients 5.x or older is not support in Horizon 8.4 and may cause performance issues.
Make sure to check the Horizon Client version embedded on any thin or zero clients. That detail buried in the firmware of the devices was the key to isolating and resolving the issue.
