Yeah, so the Online Player will happily deliver sound regardless… even if there is a break in internet connection from you to your players… the sound on THEIR computers will keep flowing (which is one of the really good things about the Online Player).
So SOMETHING is causing your computer to stop sending your voice via whatever chat thing you are using.
I do know, that chat things endevour to CANCEL noise (for the reasons listed above)… I suspect that your voicething is cancelling your voice when there is plently of noise in the room (ie Syrinscape playing loudly).
Does that make sense?
NOTE: DMing using the Master UI would be VERY UNLIKELY to make any difference to the operation of other software on your system = it is literally just like browsing on a web page…
Though… it does use a bit of up and down traffic (to show the nice spinners and amplitude feedback etc)… is your internet connection prone to being slow sometimes?
Have you tried controlling Syrinscape from a different device on a different network. Does that make a difference?