Intermittent ping lost for 32sec with C7000 and FlexFabric

[Albert3009]

We have a C7000 chassis that has 2 HP VC FlexFabric 10Gb/24-Port Modules.

Each FlexFabric Module has 3 x 10GB uplinks (X5-X7) configured for LACP and used as SUS (see attachm.)

X1-X4 are used by 8GB SFPs

Firmware is 4.45

We run some blades with Linux & Windows 2012 and found that intermittent we have lost pings. If this issue comes up, we face a disconnect for always 32sec. Wenn ping comes back, all's normal for 1day or some days or more than a week. Since we have more than one blade with different O/S, we don't think it's O/S or driver dependant!?

Uplinks are ending at 3C switches. LACP timer on both (VC and SW) are set to 'short' 1sec

Patches are:

VC1/X5 & VC1/X6 -> SW1             VC1/X7 -> SW2

VC2/X5 & VC2/X6 -> SW2             VC2/X7 -> SW1

Dont worry about the port status in my capture. X5/X6 are currently disabled for test, however in normal stage, all show 'linked active', what indicates for us LACP is well configured and LAG works over logical switch 

Wondering about ping lost for always 32sec, I'm asking if this indicates something 'well known' to you??? 

Many thanks in advance for any useful hint