Computer issue, Motherboard or PSU?

So I've had these issues, I initially thought it was the PSU due to not enough power 500w, however I think all the symptoms are pointing to the mobo maybe?

USB 2.0 failure at completely random intervals. (Only have 2 for mouse and keyboard)

Ram slot failures of 3 (except slot 4)

It doesn't crash.

Slows down randomly (however this issue can only be recreated by my missus, I don't know why it never happens when I use it and I do a lot more heavy things)

If it was the PSU it would only fail under max load right?

*Note I was cheap and used a case+psu combo which I know is a big no no.

Spec's

Mortar Artic B350

Ryzen 5 1400

8gb Ram (was 16 before failure)

GTX 6gb 1060

2x 1tb WD green (they were free)

1x 256gb Samsung evo 960 Nvme

Cougar ST-500 PSU

That sounds like a motherboard issue, that psu should be "ok" to handle that system.

500W is plenty for your setup, however that doesn't really rule out PSU problems.

It would be great if you had access to a spare for testing.

Also I found this: https://www.techrepublic.com/article/learn-to-troubleshoot-power-supply-problems/

@pyro1245: Don't have anything spare,

I tried the beta bios and my ram slot started working again, so I replugged the mouse back in to the usb 2.0 and so far hasn't disconnected, so hopefully doesn't happen again.

This sounds like the Motherboard issue and the PSU is fine cause for those specs alone won't hurt the PSU despite 500w could be better later. Also, did you try updating the MB bios at least?