I wonder how long this has been going on. The Patriots sure turned their season around after a 2-2 start and a 30 pt loss to the Chiefs in week 4. Perhaps Brady was losing his grip... Pun intended.
We can probably go back to 1967, to super bowl I, and discover that they did it then.
From what I saw, the Colts first raised the issue in November. The Ravens chimed in somewhere along the line. But if you don’t do it during the game, no way to prove or disprove it.