NON-standard-problem with remote lock caused by stereo?

Finally I found time to get the job finished.
I tried to find a hole for the power cable, so I could connect the active subwoofer directly to the battery.
...but the weather was still too cold, or I was too lazy (or maybe both).

From the beginning I had connected the black cable to the frame under the drivers seat, and it still is.
I ended up connecting the red cable to the right side 12V accessory socket (cigarette lighter).
Every thing is now working as expected.
Power to the accessory socket and subwoofer is killed when I remove the key, so the sub cannot discharge the battery.
My remote key is working every day and I see no new problems with this setup.

Thanks a lot for your answers and suggestions.

Best regards
Jan

Great. Thanks for the update