Can you guys be more specific what you mean when you say it crashes? Did the program quit/shut down, or did it just sit there saying it was trying to sync but no progress?
I am on Mac using OS 10.13.6 When I first downloaded Rig Manager and plugged in my Kemper with USB it tried to sync and just sat there not updating any synced rigs. I just unplugged the USB cable from my Mac and the plugged it back in and the sync worked very quickly, no issues since.
I always start my Mac first, then start Rig Manager and THEN plug Kemper into my Mac.
Also try a different USB cable and make sure you are using the correct USB out on the Kemper .
The process initiates and runs up to 420 rigs synced and then Rig Manager just closes and Mac asks "Ignore or send" etc then whenever you load rig Manager it bombs out immediately... that's all, I hope it makes sense. I reverted back to previous OS on Kemper and loaded previous Rig Manager and then all is well so I don't think it is usb cable or such..., thank u