If I play faster than regular speed with the "L" key, I can play for a bit but then I get a pop-up saying the plug-in crashed. Canvass goes black. I have to restart FCPX.

Also, not sure if it's related but on my timeline there are many big chunks where the preview thumbnails in the clip are just black. When the footage plays on the timeline it's not black though - unless I get that plug-in crash. Which has happened several times in the first few minutes I'm back using BRAW Toolbox.