Assistant swapping out players?

I often holiday matches when they don't really matter, like for example when I've won the title and I just want to give some youth players a run-around since the match doesn't matter anymore, and I'd rather save my best players for cup finals etc. So why does it seem sometimes even though I have it checked to use the line-up I suggested that they don't always go with the exact line-up? they'll swap players out, players who are 96% fitness, and in a good position, for no reason at all for a more established player. It really annoys me, I'm trying to just get some players some time, I don't even care if I win, it's more about giving them some experience in the first-team side.

Is this a bug? or am I completely missing something? I definitely have it checked to use the players I picked.

Edit: Sorry, a second search found this to be known issue, guess I need to be more careful before posting.

Easiest way to avoid this? Pick the team and tactics you wish to use, THEN holiday at the pre-match screen.

Ah, I'll try that, thanks.