no sound from analogue synth after closing project

Hi! I have a problem using my Prophet 6 with Logic Pro: I‘m using it as an analogue synth via audio to UAD Apollox6 and at the same time as a midi controller keyboard via USB. The problem I get is the following: when I close a Logic Pro Project, either by cmd+w or by cmd+q, the Prophet stops producing sound. I have to turn it off/on again, to make it work again. MIDI keeps going out so that works.

Anyone here has an idea what could cause the issue?

Thanks in advance!