chieftec cft-850-14c sudden shutdown with or without load

[montarbo]

Dear members,
PSU which was used in PC since 2010 without problems. Recently I started getting random sudden shutdown. I narrowed it to the PSU. Unit tested in Another PC with same behavior, the PC itself runs without problem with Another PSU.
The unit itself has CM6800G on the hot side on a daughter board. Protections done by PS229 and WT7518D on the cold side on another daughter board which also has fan control.

The psu works fine for 10-15 min at load but shuts down either under load or as soon as it goes to idle, sometimes even without any load just shut down at idle. All caps on main board measured within specs (on and off board measured with ESR). I changed the caps on the protection board but they where all good just to bee sure. Still the same with shutdowns. Added a resistor in parallel to resistor in series with PGI of PS299 and raised the voltage from 1.16v to 1.32 volts. Changed PS229, Still the same behavior.

Monitored the 5v stb,+3.3v, +5v and 12v with multimeters during 4 cycles of random shutdowns, two at load and 2 at idle. Nothing strange with those voltages just zeroing suddenly at shutdown though solid 5v stb at 5.18 all the time.

The +5v at 5.19 - 5.20 at load - idle.
+12v at 12.17 - 12.11 att load - idle.
3.3v at 3.35-3.42 att idle - load.
Any ideas where to look? anyone came across same problem?

BR