Get a good two way pager alarm for the car... also is there signs of break and enter into the under ground or storage lockers? If not, then it's people in the building just driving away rather then waiting till the gate is all the way down.
Check all walk though doors in the under ground and storage area, any signs of damage or pry marks, or anything stuck into the hole to prevent the latch from locking.
I used to be on a strata for a year or two... And we were having issue's like these once or twice it turn out to be just some strret kids.... Then we found out it was a guy that lived there that was a physico