This is an odd issue I'm having and I'm not exactly sure how to deal with it so hopefully I can get some help.
I imported my footage into FCPX and when clicking on it, it shows up underexposed. When I put it in the timeline, it still looks underexposed. I took a video of it happening for anyone who is interested

https://youtu.be/1Wkw79jR3-E

I color corrected the footage, but I had a strange feeling that it wasn't actually underexposed, so I exported a clip and it looks overexposed after my correction. So the footage is normal, but final cut keeps showing it to me as underexposed. It's not just doing it to these clips either, it's doing it to older clips that I've already edited and finished up.

Any suggestions on how to fix this?

How annoying. Maybe try forcing the color space to another standard in the settings menu of the inspector?

This is an odd issue I'm having and I'm not exactly sure how to deal with it so hopefully I can get some help.
I imported my footage into FCPX and when clicking on it, it shows up underexposed. When I put it in the timeline, it still looks underexposed. I took a video of it happening for anyone who is interested

https://youtu.be/1Wkw79jR3-E

I color corrected the footage, but I had a strange feeling that it wasn't actually underexposed, so I exported a clip and it looks overexposed after my correction. So the footage is normal, but final cut keeps showing it to me as underexposed. It's not just doing it to these clips either, it's doing it to older clips that I've already edited and finished up.

Any suggestions on how to fix this?

Probably not the same but I once had terrible problems where the timeline didn't represent the exported files and it turned out the render files were completely screwing things up. Deleting all the render files that had been generated cleared it up. This was a few versions back however. I found my answer on fcp.co just by a chance reading of a post!
Good luck.

What does the waveform for this clip look like?

You probably discovered a way to deal with this by now and perhaps you can share your solution?

I had the exact same problem when switching from one computer to the next and after restoring a backup of my computer I got the dark viewer screen problem. I read somewhere it might have something to do with pro video support files not installed (or not correctly). Re-installing them might do the trick. I never got to find a solution for it since I ended up having to do a fresh install from scratch (which cleared up this dark viewer screen thingy) after messing up administrator rights.