Some GPUs have very high fluctuations in current required on their power inputs...given an issue with the PSU being a tad weak pr mainboard's inability to regulate the up to 75W of power supplied thru the PCI-e slot, or a coomnination of both that might only show up with that PSU and that specific mainboard...
I'd try another known good PSU of more than sufficient wattage first...(do NOT mix modular cables from one PSU with another, lest your burn up your components 'lickety-split'!)
Hi thanks for the advice ill definitely try another psu just incase but I have an rmx850 so it shouldn't be that but nonetheless I have no idea what the issue is really so I'll try it also it shouldn't really be the mobo struggling to supply power one of the cards I've tested with is a gtx950 so very low power draw
I'll list my specs so you can have a look and see if you have any more suggestions many thanks
I5 9600kf
32gb patriot viper steel ddr4 3600mhz c17
Gigabyte aorus pro z390
Corsair rmx850 power supply
Powercolor radeon rx5700xt
Secondary card testing the issue gtx950
Samsung 970 evo plus nvme ssd
All under a custom loop with 720mm rad space in push pull so not heat related