Possible Fortigate 92D hardware failure

Hello guys

Sorry for my English, its not my main language.

1 month ago my firewall started to drop link between internal8 and internal14 for no reason, and without any log (except link turned down etc.). On the "working" interfaces there were many timeouts, but the link stayed up. Although reboot always seems to helped the problem, but yesterday, those interfaces totally died, even reboot didn't help anything. I did hardware test, everything passed except the network loopback test on internal8-14.
I use it in a homelab, so not much traffic going through. The room temperature is around 22-24C, so it's not as hot. I even did a factory reset, but no luck same error.

Because it hasn't got any support or warranty I did take it apart to see maybe something is visible inside.

What do you guys think? I don't have any idea what should I do. Can it be saved?