For what it's worth, I had a 2016 800 SKS 155 run fine for 15 miles after a motor out rebuild go into a random mostly no spark situation. In hasing down this electrical gremin, I replaced the stator, TSS bypass, swapping voltage regulator with known good one, swapped coils & boots, and replaced all relays, I found a used '18 Pro wire harness that ended up solving my issue. I had a mechanic look at it with the Polaris Digital Wrench that kept pointing to the coil or the wire from the coil to the ECU. We traced that it seemed like a wire issue but couldn't pin it down.
Looking at the old harness taking some of the tape off I couldn't find the gremin and gave up looking. Just glad it fixed it.