Great news!
Found out that problem was only Thunderbolt cable, in some cases its not giving contact. Even if I moved it from one port to another. Replaced it - all works again.
Please be awere that this flashing is normal startup !!! (as it seems) unfortunately this is not written in manual (please put it there) and I never disconnected drive power so did not know that, thats the reason why I thoght there is problem with device. So if youre computer loosing contact, check the cables, 10 times and try to replace them, before sending hard drives to data recovery.
All the best
Priit
