What goes on here..??? Would cleaning the speedo sensors face in the rear have helped?? I would have checked the rear wheel sensor. The more shaving on the sensor, the worse it will work. All sensors have some minor shavings on them. You need to wipe them off with your fingers. If it feels like cream/paste that's normal. Cleaning off the sensor could have fixed this issue. All the shavings can throw the magnet in the sensor off
Did it throw any codes?
ABS or Triangle light flash red? No codes is good. Your sensor was probably just covered with metal shavings as the 3.0:1 FD is very new, might not have broken in yet! Wipe if off and stick it back in. This is not uncommon! You may never see a problem again.
I guess I am too late in chiming in after you having spent $$$$ for a instrument cluster?
Should it happen again with the new speedometer...try my remedy.
By the way can you explain to us a bit to about your happiness with Claude's swing arm
...what do you see and feel?
Most if not all PNW'ers do not sport a swingarm except our Eastern brethren. My ex-sidecar was as you know built by DMC...guess you're the first DMC that has one.