Same problem and same solution offered in my service center too!!

Stupid service centers inexperienced persons!!!The people saying that the problem was fixed after they disabled the gesture fail to understand that the fault in the gesture is the external manifestation of a larger problem which resides in the power button hardware. The only sustainable solution to this issue, involves root and/or custom roms. If you want to know more, reply to this quote.
PS: The service centres also tried to convince me that it is a software issue, and flash nougat over my los15.1.