In this case, I really guess the engine worked as expected, which doesn't mean that it works as we expect
The real solution, and the real bug, is the design of the training system. We should be able to select 3 players or whatever and just they need to play 48 minutes, at whatever position, or start one game at X position or something like that....most of the complaints around lineups is people trying to force 48minutes out of players.