Just in case someone else is reading this thread and face a similar issue.

Our IT guy / SAN expert contacted Microsoft. He had a meeting with them and the Microsoft engineer revised the whole Cluster implementation. He did not find anything wrong on MS-SQL and its configuration but suggested these two Os changes:

-Change the network binding order. Put HeartBeat second and SAN last (SAN was 2nd and heartbeat the last one)

-Assign fix IP values on the iSCSI initiator properties

While I was absent during the meeting, I do not understand the 1st suggestion. It is usually how I setup my Cluster implementations. I'll give a try to the second one though.