I’ve already reported this to Arturia via support, but I wanted to share here because I’ve seen a number of posts about external sync issues and the info may help someone.
I am powering my KSP externally with a DC supply, and I am trying to sync it to my Digitakt II via MIDI, while simultaneously driving my modular from the CV outputs. The KSP is also connected to my PC via USB. I noticed that sometimes my KSP tempo would fluctuate 1.5-2x the incoming MIDI tempo. After some troubleshooting, I discovered that the issue went away if I disconnected the USB cable from my PC. Plug it back in and the instability returns. Oddly enough this only occurs, so far, while my PC is off. When I turn it on, the sync goes back to normal once the computer is booted.
So, effectively, my KSP does not like being plugged into my PC while it is off. Not exactly sure what would cause this, but if I had to guess there’s some kind of grounding that’s caused by the USB when it’s connected to a device that’s powered off, while being externally powered by DC.