In match tactic changes not saving. Am I doing something wrong?

As header really….. I start the match 433, during the match I might want to go 442 or 451 and require a change of personnel, so in the next break of play I’ll enter Team Management, choose the relevant saved tactic, press Triangle to make it my Active Tactic (confirmed with Green tick and Active disclaimer) and then make the relevant subs. I would say 50% of the time, minimum, the format has remained as the starting default and now I have players in the wrong positions. Worse still, even if it has worked, I’ve likely had to pause the game again just to check that it did and as already stated, most of the time it hasn’t. I can’t fathom what differentiates between it working and it not. Any ideas?