Weird things happening...

So, I’ve got this beautiful (IMO) model of a car that I made. Not really that great, but I’m still somewhat of a noob to blender. Anyway, I have it set up where, eg, the door is the parent of the side windows, so when I open the door the windows move with it. But I’m getting weird effects when I delete a parent, clear parents, or, more importantly, try to animate anything. For example, the tires (which are children of the wheel centers) have a tendency to either swell or shrink, to 1.5922x size (or the reciprocal, if they’re shrinking) in the xyz, and 1/2x size in the x and z. ie, to fix it, I change their size to 1.5922x, and then 2x in the x and z. Also, the interiors of the doors tend to jump, rotate along the y, and sometimes mirror themselves (ie scale -1 in the y). It’s really annoying, because I’m trying to animate the doors opening. I’ve animated the doors in the past, but nothing like this has happened. I’ve cleared the parent all 3 possible ways, each time putting the objects back the way they were, and I can’t seem to fix it. It would be awesome if someone could help me.