maybe some capacitor with problem

Would the board potentially have bad caps even if they're not showing signs of wear? I've never recapped before but have a good friend that can help me, and I know the CUV4X is known to have caps issues (alongside everything else in the P3 era). I took the board out today to clean it and there was no leaking or bulging, but I suppose that doesn't necessarily mean one or two haven't gone bad.

This hardware is old enough at this point that any caps, defective or not, can be bad. If you have a reasonable suspicion probably the only way to be 100% sure is to do some "exploratory surgery" - desolder a cap or two and check them in a tester.

In my experience if they look fine they are often fine, but not always - i've seen completely dead caps with no visual indications...

I think that has to be the issue here. I've added nothing new and the system will randomly completely lock up - now even after replacing the Tualatin with the Coppermine it originally had. With that in mind, is there a good resource for what caps I might need? Where should I get them from?

my last order of components was from mouser.
Memory errors, cpu errors are most the time caused by bad capacitors. "it runs fine with 1 stick of ram, add another and crashes, freeze.."