AndyBennz Hi Andy, I am no computer programmer but was an electronic tech in the days people actually fixed equipment that had no reset buttons 😂, it sounds like when you open ST3 which is an audio player ST3 is setting up the audio engine for its own use and this is causing a glitch in your other software which is trying to use the audio engine , this could be an operating system issue not an ST3 problem, I am sure Peter is going to know what it is .
But I am curious to why and what are you using ST3 for it seems like you are doing DJ work , are you also performing live and you need to swap from the other two bit of software to ST3?
Good luck with finding a fix, perhaps update all software which you have probably done.