I thought when I read your initial post and what you tried to start with, probably the CPU, more specifically I think it sounds like the memory controller on the CPU, we'll never know for sure though I guess.
On a side note but related to your memory, running 4 x 32GB sticks on a Ryzen CPU could be challenge period even on a CPU with a good memory controller as that's a lot of load on it, 4 x 32GB sticks, those are all going to be dual rank DIMMS (chips on each side of the PCB) and so that's 8 x ranks, Ryzen doesn't like 4 x memory modules much at the best of times, even when they are single rank sticks, you might be able to get it to be stable but you'll probably have to lower the speeds, I doubt EXPO will work in all honesty, hopefully it does work for you though.
On a side note but related to your memory, running 4 x 32GB sticks on a Ryzen CPU could be challenge period even on a CPU with a good memory controller as that's a lot of load on it, 4 x 32GB sticks, those are all going to be dual rank DIMMS (chips on each side of the PCB) and so that's 8 x ranks, Ryzen doesn't like 4 x memory modules much at the best of times, even when they are single rank sticks, you might be able to get it to be stable but you'll probably have to lower the speeds, I doubt EXPO will work in all honesty, hopefully it does work for you though.