Alarm system and electrical problems

My '03 525i has just passed 50,000 miles - it drives beautifully....BUT...

The alarm goes off every few minutes once the door is locked (which activates the alarm) and then by the am commute, the car battery is drained requiring a service call or towing.

The above problem had occurred when the car had 18,000 miles on it. Because the car was covered under manufacturer warranty, the BMW dealership addressed the problem by keeping the car for one week, running diagnostics and replacing sensors then returning the car indicating it was fixed. That weekend the problem recoccured, the alarm went off all night, the battery was dead, the car had to be towed and the car was in the BMW dealership for one further week again for diagnostics and sensor replacements. After two weeks in the shop, I thought the problem was fixed.

Now, at 50,000 miles, the alarm is going again. And, the icing on the cake, a service person offered his opinion that fading and flashing electronic readouts on the dashboad were indicative of pending electronic failure that, in his opinion, would cause an odomoter failure, then an odomoter replacement and TMU (true mileage unknown after the odomoter replacement even if done by BMW).

Has any one ever heard of recurring electrical problems after they have been "fixed" in a BMW dealership? Is this service tech's opinion on or off the mark? And, what suggestions do you have to resolve the above.
Thanks all.