R129 sucks battery empty

Hello together, I have the problem with the SL that the battery is constantly unloading itself in the stand. The problem has occurred for about 5 months so that after 1-2 weeks of service life the (charged) battery is so unloaded that the car can no longer be started. Probably the alarm system sucks the battery empty, because the discharge time is extended in the case of an unfinished car. Bosch service has measured and found nothing. Battery is apparently also ok, Lichmaschine also. n instead a 12V can connected to the battery. So I can have the car connected to the maintenance charger in the garage. Their comment was that the problem with the SL is completely normal and that happens to many. Therefore my question to you, whether you have this problem in principle? I don’t think it is normal that you can no longer start the car after 1 week of service life. It is a 95 R129 SL 320. Nice greeting to all SL friends