Troubleshooting - 2nd PSU turning off at random?

Firstly thank you to anyone taking the time to read/reply!
I’ve just built my first rig to test out before i go all in!
The rig consists of:
Biostar TB250 BTC Pro, 4 x RTX 3070 TI, 16GB corsair ram, 480gb sandisk ssd, 2x Corsair HX1200 PSU’s
(and 4 risers) - running on HiveOS, mining RVN, (OC - Fan: 100 Core: 100 Mem: 2000 Power:230)

Each PSU Powers 2 risers (split off 1 PCIe cable) and 2 GPU’s (2 PCIe cables each)

The second PSU (only 2 gpu’s and risers) seems to be turning off at random, after 2-9 hours but will turn back on as soon as i restart the rig with no issues, i’m monitoring the power drain at the plug and i’m well within the 80% limit!,

So for i’ve attempted to unplug a GPU and see if it still has an issue, which it does, the only thing i haven’t swapped out are the risers - am i safe to say after that test its a faulty PSU or could this be an overclock issue?

Any suggestions would be much appreciated!

(not sure if its important but i’m using a 24-Pin ATX Dual PSU Power Supply Splitter Adapter cable instead of the safety pin trick)

Thanks in advance!