Connection resets at SSL/TLS level from F5

Context- We have load tests executed from Amazon cloud instance (source) to aaccess application through f5 hosted in-premise and images/Js/cc are hosted in CDN and application data and few images are served from In-premise servers. All requests are in HTTPS and connection uses TLS 1.2

 

Problem: We notice that when users are ramping up from 2K to 3K users (more connections opened from client to server) client is waiting for the response from server and later client throws encrypted alert 21 (happening at TLS layer) followed by connections resets and retransmission failures.

 

Captured through wireshark but not able corner the problem (attached the snapshot)

 

Last it worked well on June 26th Test and July 3rd first occurrence of this errors.

 

what changed in between and suspects that could be contributing,

 

1) Firewall configuration changes due to vulnerability exposed at TLS/SSL layer 2) POODLE attacks fixes on F5 3) within Amazon cloud infrastructure

 

Any inputs to investigate in right direction will help us a lot.