Just purchased a 320i 2010 touring m sport

seems to be an intermittent problem with the remote locking , one minute it works, literally 10 mins later it doesnt? (both fobs)

contacted stealer i bought it from, and according to service dept its a common fault under the roof spoiler?

so its booked in on the 3rd of feb to be repaired

im thinking its the remote being out of charge due to being on a car lot for past 3 months? because after any fairly lengthy journey the remote works????

advice opinion please