iMovie Causing my MacBook Pro Screen Glitch...

Hello everyone,

I updated my iMovie to v10.1.13 last week (finally caved after being constantly reminded to do it), and it worked fine for the most part, but when it came time to export the video I was working on, it caused my screen to go all glitchy (specifically when I clicked on a drop-down menu or one of the top menus).

I took some screenshots, and though you can see there is some glitching, the actual glitch looks much worse (I blurred out some sections, please don't mind those):

My MacBook is a mid-2014, 15" model that is currently running Mojave (10.14.6).

Any help would be great, or if someone could point me in the direction of how to rollback my iMovie to its former version (I didn't do a Time Machine before I updated – it was a careless mistake), it would be much appreciated.

Thank you in advance, and all the best.