Yatour pulls battery empty?!

Today too, today again one of the stupidest situations you can have… Mummy calls: “Can you come to me to work and help me get started? I let the light on…” Innerly joy that something like that doesn’t happen in the Volvo and promises to happen. With keys to Volvo, pressed on Unlock. Pressed again. Unnerved with keys unlocked (as I later noticed only the driver’s door…). Locks in ignition lock, clutch kick, keys around and… silent. Dead nstille. I drove the last time on Wednesday and also retrofitted the Yatour, then the moose stood there until this morning. Doors were closed, so interior light didn’t pull out. Otherwise he always managed to survive more than 2 days without movement, so I push the black Peter to the Yatour interface. How did I install it? Quite simply, fuse out, radio out, permanent plus with current thief on A12, CD changer plug on it, radio back in again, fuse re in, radio code typed in, worked. Strangely at least: if one turned off the ignition in Yatour mode, the radio remained still so 5-10sec. and continued to doddle until it turned off after all. Any idea what I can do about it or what I could have done wrong? Oh yes, what I did with my SC-805: soldered the AUX-In. But this has been working smoothly for a few months now, so I actually exclude it as a cause.