FCPX suddenly seems like it's running on a G3 using a Class 4 SD card for a hard drive

Not sure why but this project I'm working on has FCPX flippin' out. I have a lot of retiming going on. Project isn't very long but the source clips are. They are all ProRes and on the same RAID drive that all my other Libraries live on. Disk performance is still awesome. But when I select Optical Flow I get a spinny wheel and the system locks up for quite some time. Just doing anything in the timeline even copy/pasting takes an incredible mount of time. Windows 3.11 is faster than this. Oh, and if I zoom in or out of the timeline it doesn't like that either. Does FCPX just not like long files or something? This is the only thing that I can think of that's different than my normal projects.

Latest version of FCPX. Latest Yosemite. Latest Mac Pro. Etc etc etc. There's gotta be something askew somewhere.

EDIT: Oh, and this project has LOTS of cuts. Well over a hundred so far in a 3 minute space.

When things bog down for me (and they frequently do) I check the Background Tasks window in FCP to see if it's doing a lengthy analysis and look at the Activity Monitor app to see what else the computer might be doing. Choosing Window/Revert to Original Layout sometimes perks things up (the inspector window for some reason seems to especially slow things down), and when nothing else helps I restart the Mac.

Well the zooming in and out of the Timeline problem was caused by having so many cuts/clips in the video. Turning off thumbnails fixed this issue. I wish there was an option for a single thumbnail at the beginning of each clip like in FCP7.