Maybe it is not the same but I had issue that the F5 and the servers may have different time_wait for connection reuse as for f5 is 2 seconds by default and you may change this for the newer tcp profiles to match the servers as their time_wait could be bigger or smaller (for windows servers it is much bigger):
https://support.f5.com/csp/article/K29377715
For fastl4 there is still no such option and adding a SNAT pool with many ip addresses and maybe preserve the source port for SNAT:
https://support.f5.com/csp/article/K14400019
Also randomizing the ports helps but this are system variables, so be carefull:
https://support.f5.com/csp/article/K8246
https://support.f5.com/csp/article/K46113533