You cannot scale a terrain a frame after creation, at least with chunked terrain. (Why use wait(1) anyway?)
The (german) manual says unchunked terrain can only be 128x128 vertices big, not sure if that's a hard limit or a guideline and 130x130 is still fine.
If nothing works and you don't want to use chunked terrain you can still convert your terrain to a model and load it as that.