Are you using async loading? Another customer was having an issue with this, and I was hoping to properly fix it in the next update. The temp solution I told them was to use FindObjectsOfType() and call Rebuild() on all of the meshes, but that's weird that it's not doing anything for you. The cause probably has something to do with the OnSceneLoaded delegate on STM.
Does it still happen with non-UI text? That might help me narrow down the cause.