Some coils are a lot more prone to electrical interference than others. Usually, the bigger the coil the more prone it is to EMI problems. I would assume the 5.3 or the 4x6 would be some of the best choices of coils to use in that area. What coil did you use?
Also, Relic mode has 2 different preset SAT speeds that you can try that will calm down the chatter. Depending on what model you have, MXT or MXT PRO, you access these 2 modes differently.
On the MXT, in Relic mode, the trigger position(center or forward) switches between the 2 modes.(fast/slow SAT speed)
On the MXT PRO, in Relic mode, the Tone ID ON/OFF switches between the 2 modes.(fast/slow SAT speed)