got a support ticket created with F5 :
realized that the TIME ZONE or a difference of time between the switch and load balancer could not be a cause of the failover event. Indeed, if so, it would have occurred again in the past 2 months since it happened last time.
Some evidences in the logs really pointed to a switch port fault and then, the load balancer triggered a failover event, which is expected.
At this point I do not recommend any changes on Load balancer time zone settings and if this event occurs again I would recommend to check the switch´s ports and LACP transactions (status/logs).
Anyways we are gonna close this for the time being and monitor if it happens again...
thx guys for the help