We're aware the arduino-cli doesn't behave that well when multiple instances are running in parallel as of now since they all use the same environment, but I wouldn't expect your case to be one of the problematic ones. Thanks for the heads up anyway.
Also for future issues would be great if you could open them directly on the arduino-cli Github repo, it eases our job of tracking them. Hopefully you'll have no further problems but you never know. 