It really does depend on who acts first.
Thanos # 2 can't stop time if Thanos # 1 blinks the gauntlet away from Thanos # 2.
However, if Thanos # 2 does go back in time before Thanos # 1 can perform said act, then he stops Thanos # 1 from putting the gauntlet on in the first place.
Which of them is the real Thanos?
Because that one takes it.