T320 power error PSU003 although power was restored

Hi,

repeatable symptom on my first T320 power (750 W) :

PSU1 and PSU2 are in redundant mode, both green and connected to UPS
i unplug PSU1 -> turn yellow -> plug again -> turn green   ok !
the same on PSU2 :  i unplug PSU2 -> turn yellow -> plug again -> remain yellow permanently
then manual shutdow server
then power on :  both green (!)

is there an hardware or firmware issue ? on my  second T320, all PSU turn green after plug

see below board firmware / part nbr :

First T320
PS1 OK 09.2B.80 09PXCVA02
PS2 on error 69.45.99 06W2PWA01

Second T320
PS1 OK 09.2B.80 09PXCVA02
PS2 OK 07.2B.7D 05NF18A01

Bios on both servers :  2.9.0

Last dell firmware available for  6W2PW is  69.45.9B

thanks for your review