Win 2008 R2 cluster quorum disk 'disappeared' temporarily

It's just plain SAN LUNs that's presented to both servers.
We have similar setup at a few other sites' clusters but
did not encounter this issue.

This issue is not persistent, ie it happens every couple
of weeks or months

I've done  "cluster /prop" & below is the output.  Compared with all other
clusters & only one line (EnabledSharedVolume) is different from other
clusters (except I have one DR cluster which is also 1 but never had
this issue):

Attached are the cluster.log files from both nodes of the cluster
which I've sanitized: look for 2003/12/16-11:50  to  2003/12/16-12:00
date & timings

Listing properties for 'NNXXXPP1VIR03':

T  Cluster              Name                           Value
-- -------------------- ------------------------------ -----------------------
DR NNXXXPP1VIR03        FixQuorum                      0 (0x0)
DR NNXXXPP1VIR03        IgnorePersistentStateOnStartup 0 (0x0)
SR NNXXXPP1VIR03        SharedVolumesRoot              C:\ClusterStorage
D  NNXXXPP1VIR03        AddEvictDelay                  60 (0x3c)
D  NNXXXPP1VIR03        BackupInProgress               0 (0x0)
D  NNXXXPP1VIR03        ClusSvcHangTimeout             60 (0x3c)
D  NNXXXPP1VIR03        ClusSvcRegroupOpeningTimeout   5 (0x5)
D  NNXXXPP1VIR03        ClusSvcRegroupPruningTimeout   5 (0x5)
D  NNXXXPP1VIR03        ClusSvcRegroupStageTimeout     7 (0x7)
D  NNXXXPP1VIR03        ClusSvcRegroupTickInMilliseconds 300 (0x12c)
D  NNXXXPP1VIR03        ClusterGroupWaitDelay          30 (0x1e)
D  NNXXXPP1VIR03        ClusterLogLevel                3 (0x3)
D  NNXXXPP1VIR03        ClusterLogSize                 100 (0x64)
D  NNXXXPP1VIR03        CrossSubnetDelay               1000 (0x3e8)
D  NNXXXPP1VIR03        CrossSubnetThreshold           5 (0x5)
D  NNXXXPP1VIR03        DefaultNetworkRole             2 (0x2)
S  NNXXXPP1VIR03        Description
D  NNXXXPP1VIR03        EnableSharedVolumes            1 (0x1) <==
D  NNXXXPP1VIR03        HangRecoveryAction             3 (0x3)
D  NNXXXPP1VIR03        LogResourceControls            0 (0x0)
D  NNXXXPP1VIR03        PlumbAllCrossSubnetRoutes      0 (0x0)
D  NNXXXPP1VIR03        QuorumArbitrationTimeMax       20 (0x14)
D  NNXXXPP1VIR03        RequestReplyTimeout            60 (0x3c)
D  NNXXXPP1VIR03        RootMemoryReserved             4294967295 (0xffffffff)
D  NNXXXPP1VIR03        SameSubnetDelay                1000 (0x3e8)
D  NNXXXPP1VIR03        SameSubnetThreshold            5 (0x5)
B  NNXXXPP1VIR03        Security Descriptor            01 00 04 80 ... (280 byte
s)
D  NNXXXPP1VIR03        SecurityLevel                  1 (0x1)
M  NNXXXPP1VIR03        SharedVolumeCompatibleFilters
M  NNXXXPP1VIR03        SharedVolumeIncompatibleFilters
D  NNXXXPP1VIR03        ShutdownTimeoutInMinutes       20 (0x14)
D  NNXXXPP1VIR03        WitnessDatabaseWriteTimeout    300 (0x12c)
D  NNXXXPP1VIR03        WitnessRestartInterval         15 (0xf)
DB1clusani.txt
DB2clusani.txt

> are your NIC configured to go to sleep - this is a default setting under the
> NIC power management setting, turn that off.
No, certainly it's not, else I would have got Tivoli alert for ping
timeouts to both DB servers'  teamed NICs' IP addr.

>  validate your cluster as that may highlight some issues
We have run this & only a couple of warnings with the rest
Successful.  I can post it this Mon/Tue after sanitizing the
outputs.  For sure, it's the same result as when we first
install the cluster & if any of the error/warnings are serious,
cluster installation would not have been allowed by Windows
in the 1st place, right?

Yes, all components have been rebooted.

Well, I'm not sure if it's really necessary to apply the hotfixes as the
other sites' cluster uses exactly the same Win 2008 R2 with same
patch level.

Only difference is the hardware type & firmware revision:
this site uses a slightly newer version of IBM x3850 hardware
compared to the others sites that are stable.

Is there anything we can analyse from the logs to pin-point
the root cause so that we can come up with a sure-fire
resolution?