Child's position not moving with parent?

I'm trying to get my character to move along with a moving platform. I'm trying to do this in a platform.cs script where onTriggerStay() causes the character's parent to be set to the platform.

I have done this in a previous project and it worked fine, but now the character doesn't move with the platform at all. If i disable the CharacterController then it works fine, so I'm thinking it might be something to do with calling the move() function but I can't be sure.

Can someone help? I'm out of ideas here.