UnityVSA pool shows offline

Hello everyone

I have UnityVSA-5.1.0.0.5.394 running on my lab

I have created 7 vmdks:

one 32GB on an NVME2 disk and put it on "Extreme Performance Tier"

three 100GB on RAID_1 SSD disks and put it on "Performance Tier"

three 256GB on an external USB_HDD disk and put it on "Capacity Tier"

with all disks I created a 1TB Pool then added 2 LUNs, the first 100GB Thick and the second is 900GB Thin.

up to here everything runs smoothly and as desired.

When I put the two LUNs into heavy writing load, the SPA reboots and I end up with both LUNs fails along with their Pool and the Pool goes offline !!!!!!!!!!!!

Can someone give me a clue what is the problem ?????