Multipath error

[XMlabs]

Hi,
In my enviroment I have a SAN storage connected to my proxmox nodes with 2 different fabric and each node is connected on both fabric.
Obviously I have configurated a multipath service on all node but if I reboot one of the fabric in order to test the failover all of my proxmox nodes and vms go in uknown state, the cluste keep "ok" status and vms continue running but are all in unknown state.
watching in syslog I see:

Feb 07 13:05:12 phv02 multipathd[27446]: SAN: sdc - path offline
Feb 07 13:05:14 phv02 multipathd[27446]: SAN: sdc - path offline
Feb 07 13:05:16 phv02 multipathd[27446]: SAN: sdc - path offline
Feb 07 13:05:18 phv02 multipathd[27446]: SAN: sdc - path offline

then I restart multipath service on all node and all is ok.

this is my multipath.conf:

defaults {
        polling_interval        2
        path_selector           "round-robin 0"
        path_grouping_policy    multibus
        uid_attribute           ID_SERIAL
        rr_min_io               100
        failback                immediate
        no_path_retry           queue
        user_friendly_names     yes
}

blacklist {
       wwid .*
}
blacklist_exceptions {
        wwid "2346263353666332d"
}
multipaths {
        multipath {
                wwid "2346263353666332d"
                alias SAN
        }
}

I've done all step described here: https://pve.proxmox.com/wiki/ISCSI_Multipath
I would to know, is it normal? there are anythings that I can do in order to avoid to restart multipath service when a channel go offline and then come back ?