My suggestion, if you have a way to do so, would be to try that graphics card in another machine that DOES have a suitable, known good power supply in it OR a different graphics card in your machine, to see if the problem persists either way.
Alternatively, simply replacing the PSU is probably the least expensive way to throw something at it to see if it sticks, and is probably the most likely cause of the problem anyhow. At five years old (IF it is, since most reviews of that model are from 2016), that power supply is well into the age window where problems are likely and it could simply be a prematurely defective unit as well. Or, it could certainly be the graphics card itself. Even the motherboard could be to blame.
Without swapping parts in or out to eliminate some potential candidates, it's really more of a guessing game, but given the age of the power supply and the fact that the OEM used for those V650 units, Enhance electronics, doesn't have the greatest track record when it comes to build quality and longevity, it wouldn't be too surprising to find that it's the problem at all. I might start there no matter what, simply because it is probably a good time for that to be replaced anyhow and since it's a likely culprit, that might drastically shorten the troubleshooting process.
Do not however be too surprised if the problem is something else OR is more than one thing. Often with a failing power supply it's not uncommon to find something else has been affected as well.
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