Oh yeah! Finally got it.
Went full on brute force mode after not getting anywhere after replacing the UC3844. Decided to remove all the caps and replace them, just in case. Even though they looked "good" I know they can still be bad. They even read good, but still, wanted to go for it.
And behold, one of the 1000μF 10V caps showed a tiny bit of leakage on it's other leg (see picture). Replaced them all, machine works again. Thank you all for the input.
I feel super stupid for not doing this right away...