Fatal1ty AB350 random freeze (USB/M.2)

I scanned through the forums suggesting downgrading my BIOS but I didn't buy that.
I did several test by disconnecting the HDD , SDD and M.2 onboard disk.

I noticed: with M.2 on board : even Ubuntu Live CD would get hung sometimes.
just freeze the screen. only way out was to cut power.

What I noticed as well is that booting the MB to an SSD with Windows OS worked just fine. no errors or freezes.

so I started suspecting the M.2 compatibility with firmware 6.x

what seems to solve my issue was to change the BIOS CPU settings for M.2 : from auto mode to Gen1 compatible (other menu options were gen2,gen3).

With that settings alone I was able to boot my M.2 disk with no freezes so far (2 hours and counting...)

so my advice: if you encounter strange behavior with ASRock Fatality AB350 MB and 6 firmware : try

go to Bios --> Advanced tab --> AMD PBS --> M.2 PCIe Speed --> set to "Gen1"
save & reboot.

so far it fixed my disk freezes.