RST/ACK sent by F5 loadbalancer to the client

yes, I made some tcpdump capture on the F5 to analyse more precisely the observed behavior. It's clear that the RST come from the F5. I checked health monitor and logs, and the server is always available.

My architechture is the following: (A)IP client <-> (B)IP VS - (C)IP back F5 <-> (D)IP server

I have two scenari of failure: first one connnection is established (at TCP level) and client/server are chatting during 10 sec there is no more traffic on the TCP connection D sends a FIN,ACK to C B relays the FIN, ACK to A A reply with an ACK to B B sends a RST,ACK to A <= this is my problem

second one: connnection is established (at TCP level) and client/server are chatting during 1 sec there is no more traffic on the TCP connection A sends a HTTP POST request to B B sends a RST,ACK to A <= this is my problem

If you want I can send the tcpdump (1Mo each)

Regards,