The point is, if you are sitting in the same, or roughly the same, area... Part of the structure may be absorbing signal. T-Mo's frequencies do not penetrate well when structures are made of brick, CEMENT, etc. Steel reinforcements further hinder the signal.
I understand that Yankee Stadium is open air, but you still may benefit from a change in location within the stadium. For instance, if you usually sit on the Jerome Avenue side, try the 161st St side. IDK where the towers are and you are vague about where you sit. "Up top usually," does not offer me anything to confirm or deny my theory. You can actually search tower locations and check if the stadium would block signal at your normal seats.