Can you please suggest best load balancing method that works well with source address affinity persistence?

Thank you. Currently, the algorithm we are using is round robin and the users are directed to a different application server sometimes from the middle of their job or immediately when they login though the source address affinity is set for 30 mins and we are doing ssl offloading on the VIP with 4 backend servers(no certificate on them). This setup was working fine before and this issue had started very recently.

The error they are seeing is FRM:92104 which is very intermittent. Please let me know if you need more information. I am unable to figure out if this is a load balancing issue or server issue.