In the session logs you see "Interthread queue is full" messages.
There are inter process threads between SSLdata and the HSM (Hardware Security Module). "Interthread queue is full" messages are related to HSM instability in the network and in the logs you will generally see messages related to the HSM flapping and or messages like "HSM network connectivity failure" in conjunction with the "Interthread queue is full" messages.
- Use IP's for HSM connectivity configuration instead of hostname, especially so if you are running a 3.x version of SSLV OS due to bug related issue with HSM's in 3.x versions.
- Depending on the amount of resigns per second you may need to modify the number of connections to the HSM. Generally reducing those.
- If not already on 4.x software, upgrade to 4.x