Did you try switching my.polygon to on now?
There are many factors that could cause your player to get stuck, but we don't know enough of your terrains, models and scripts to tell you what might be the error.

We don't even know the 3dgs version you are using. There has been a bug report about models getting stuck on bumped areas on blocks (not models or terrains) but it could be related. If you start testing why, when and where it gets stuck, we and perhaps you too find the cause for it.