What does the terrain normally look like? A screenshot from the 3D view in WM would be helpful. My guess is the altitudes have been significantly increased (multiplied) in TG. WM's TG output has long had an issue with improper scaling. I'd suggest trying potentially some other output format like TIF, or just use a Heightfield Adjust Vertical to precisely match the indicated elevation range *in WM*.
- Oshyan