Since I’ve had my One set up in the following way I’ve had no stuck notes or any midi sending weird stuff onto other devices, as my One is master controller for everything.
I have the midi in set to din midi and the USB for midi out. When I was only using the USB for midi in and out, the One was making lots of things behave weirdly. Also making the One crash. So if anyone still having trouble try these settings
This sounds very very (very!) much like you had a MIDI loop to and from your ONE, where all MIDI out data was echoed back to the ONE. The symptoms you describe are exactly what you would experience in that case.
Using the two different types of MIDI I/O got rid of it.
I only use USB and and it works equally well as the DIN.
Have you tried using DIN for both in and out? I’m curious if you’d see the same problem(s)…