Consistent failures on new AMD Radeon 5700 XT

I can understand your frustration but  "can't run any" or that you have "Consistent failures" as your thread title suggests, is perhaps not the best description :-).

I had a look at all 273 tasks assigned to your computer, 233 GW GPU tasks and 40 GRP GPU tasks.  For the GW tasks, 214 were aborted, 11 were deadline misses, 5 were validated and there were only 3 actual compute errors.  So the ratio of 5 successes to 3 failures seems to suggest that the software/firmware/drivers side of things is OK and that perhaps you have some sort of transient hardware issue, despite the stress testing that you have already done.

It's a similar story with the GRP tasks, 38 were aborted and there was 1 valid and 1 actual failure.

Of course the failures are not acceptable so you need to do something.  I don't know what sort of relationship you have with your hardware supplier, but the first thing I would try to do is beg/borrow/steal a known good PSU to see if that solves the problem.  In the process of testing the PSU, make sure you pay particular attention to all connectors to make sure all devices have a good electrical connection.  The other easiest items to test are memory modules and the GPU itself.

Change things one at a time so you know exactly what is to blame if you suddenly get a string of good results.  If your GPU is relatively new, your supplier might be quite willing to lend you a replacement in order to verify if you have a warranty claim or not.

When you are ready to test, make sure you have a very low work cache size so you don't have to abort hundreds of tasks if the failures continue.  Good luck with finding the problem.