Dual PSU issues after power outages

[nitrobg]

My setup is the following:

- Regular PSU to power only the motherboard+CPU
- Server PSU to power all GPUs, both riser+8pin
- Regular ATX motherboard
- Not connected the grounds of both PSU
- Both power supplies are connected to the same power outlet

The rig works perfectly well when I disconnect the power from both units, wait few seconds to discharge the caps, connect the secondary (server), wait few seconds, and then connect the main one. However after a power outage, both supplies start at the same time and the rig is unstable (boots fine, detects GPUs but hangs after I put load on them) until I manually disconnect both and repeat the procedure.

I know about Pico PSU, but I'm CPU mining as well and those mini boards are not designed for a high load.
How do I solve this issue without replacing either of the units? Perhaps connecting both grounds would help, but I haven't tried that yet.

[1713256101]

1713256101

[1713256101]

1713256101

[vuli1]

i have no such problem. atx psu give power to everything, including pcie risers, server psu give power only to pci-e x6/x8 connectors.