Dropping .gif into timeline crashes FCPX / converted videos black on import

So after I copied the uncrashing project elements into a new project AND reset FCPX, I noticed I could now see inside the original .gif files (those that were left in place at import, on the same USB drive as the event files) and FCPX could process them after I dropped them into the timeline. So I'll work with that because I don't want degraded quality.

In ffmpeg I didn't use any special settings, just ffmpeg -i original.gif output.mp4 or .mov. I have ffmpeg built so it includes the commercial codecs.

I had imported 100+mb .gif files before but this project has .gif of 300 to 770mb. They are all now imported successfully and I dropped them into the timeline.

As for testing you just need Universe Sandbox and export animations to .gif of increasing size untit your computer crashes. Pity Universe Sandbox doesn't offer any other export option than archaic .gif.

Going from bad to worse, after resetting FCPX and re-importing the original .gif into another library, copying the files, the copied files are all black as well. In the original library where I imported them the first time, I just realised though a thumbnails shows up, displaying a middle image by pressing space and again immediately to stop hangs the program for a while. So only the gif "left in place" at import can be seen from the browser, but the copied gif to another library show up all black.

If the gif can be browsed from the FCPX browser somehow means the images can be seen. So how do I drop one into the timeline without crashing FCPX? I already made optimised and proxy media on import.