Just purchased Pro 18. (already had Movie Studio 17).
When I load a video (any mov or mp4) in to my project, audio fine, video stutters, flickers green, is not viewable.
With Movie Studio 17 works fine on same machine with same videos (and all formats).
Uninstalled and re-installed Pro. First video loaded in to project fine, until the first split I put in the the loaded video, immediately that video corrupted, and undoing made no difference, and all other loaded (video) files exhibit the same issue, issue exists across all projects.
AMD Ryzen 5 with Radeon Graphics 3.00 GHz, 32GB RAM, GeForce Gtx 1650 4GB.
I've also re-patched Nvidia, updated Quicktime and downloaded and installed K-Lite Codec pack to try to resolve.
(Movie Studio 17 is still working fine).