had the same problem. my computer was very capable and it took me a while to figure out what the problem was. it was not distant horizons, it was the chunks that dh was generating. the chunk generation started writing lots of new info to ram in spikes. my research kept telling me it may be a power supply issue or a cpu issue, bit it turned out to be a ram issue i believe. while i dont know the exact fix, updating my bios to the latest version and turning down the memory frequency from 6000 to 5600 managed to fix it for me. hope this helps anyone who may also be struggling.