F5 Pool Members flapping issue

Change your tcpdump to

tcpdump -i 1.15 -ni vlan_internal host 10.64.32.16 and host 10.64.32.35

so you can see the response or lack there of coming back from your pool members. If they don't respond within 16 seconds they will be marked down based on the timeout of 16 seconds in your default tcp monitor. Also, have you enabled monitor logging for one of your flapping pool members to see why its being marked down? Once you do that each pool member that has that enabled will have a log at /var/log/monitors/.