Constrained grabbable rotates the wrong way

I'm trying to create a platform that can be grabbed and moved along the y axis. And the user should also be able to rotate it around the y axis. I've added a GrabFreeTransformer and I'm constraining X and Z position as well as X and Z rotation. Now when I grab the platform and try to rotate it, it rotates the wrong way around when grabbed somewhere near the edges. When I grab it towards the center it rotates as expected. I think it might have to do with the rotation taking the point where I grab the platform as anchor. Is there any way to set the "anchor point" of the grab to always be the center of the object? Or is there any other way to get the behaviour I'm looking for? Thanks!