Hi Matt. I had a scene that crashed Terragen while i deleted an animated parameter.
I thought it was related to the RTP preview. But after some testing i saw that it crashed only with HD on
and even without it too (with the right above "Renderers" menu box selected).
The common thing is, it crashes nearly every time when you delete an animated parameter when the preview is still updating.
If the preview is not updating while you delete an animated parameter Terragen doesn't crash.
There are some fixes after my version i use (4.1.25) related to animated parameter deleting crashes. Don't know if this is one of them.
*Windows 10 64 bit, Terragen 64 bit v. 4.1.25, AMD Ryzen 9 3950X, Nvidia GTX 1660Ti