Timerion's attack Time machine may be the worst to deal in the game. It gives -39% attack and switch you back to its juvenile form. The only way to deal this is to remove it by attacks that remove negative statuse but never do that, why? There's a bug and SP did admit it is a bug.
If you "Remove Negative Status" while your team is in effect of time machine, it wll change you back to adult form, yes. But then nothing else will happen, literally the game will just stand there.

It happens to my Furhem's Scourr while time machine is active and my team went back to adult form but nothing happens next, they just stared at each other. I write this problem at support and they did say that it is a bug they are fixing now.

Not many choose this skill so not much analysis about it. I suspect this is not status effect (same for stamina drain), so it can't be cleared. But only SP can confirm this.