If it’s EMI, you’ll want some ferrite cores, something like:
https://www.amazon.co.uk/Ferrite-DOKEI-Anti-Interference-Suppressor-High-frequency/dp/B095HJZFVB/ref=sr_1_4
When putting my rig together, I bought a couple packs of these, and put them on basically every cable (all power, and all USB cables), as I’d heard my direct drive wheel base was susceptible to EMI. It’s a bit of a chore, but shouldn’t be too bad.
Thinking about it, it is possible (but seemingly debatable) that you don’t want these on audio cables, which would include the cable going directly into the buttkicker, since that’s essentially just a speaker level audio cable. I don’t think it should actually be a problem, but do all the power cables first, and see if that fixes the issue. For what it’s worth, I didn’t put them on any audio cables, and I’ve never had an issue … albeit I have the G2, which you didn’t have an issue with either. Good luck.