Hi,
Check the notes for LB::reselect there is some problem:
Click here
Version Specific Notes
LTM 9.2 When load balancing fails to a selected member, the iRule LB::reselect command repeatedly attempts to connect to the unavailable member, rather than selecting the next available pool member.
See AskF5 SOL8188 (CR84102) (deb)
LTM 9.3, 9.4, & 9.3.1 When load balancing fails to a selected member, the iRule LB::reselect command repeatedly attempts to connect to the unavailable member, rather than selecting the next available pool member.
See AskF5 SOL8188
Click here (CR85186) (deb)
Maybe you can try to do a LB::detach to close the connection to the server and do the HTTP::retry