SOLVED, well sorta. I guess the better reply would be found a workable SOLUTION.
I do have compressor installed. (Latest version)
The problem only appears on multicam projects. As soon as I hit “view angles” the video starts the lag terribly.
I am running 4 1080p angles and 2 audio tracks. I do not use proxy/optimized footage. I never have, and never had to in the past with similar projects.
I’ve tried switching between original/better performance settings. No change in the stutter/dropped frames.
I tried a fresh reformat and clean install a couple of times.
I tested this on the system listed above and on a 2015 iMac. Same exact issue on both machines.
I started deleting apps that I usually run just to see if anything was causing it. Adobe, Firefox, mail, Slack, you name it… No changes in the crappy performance.
So I once again did a reformat/clean install of High Sierra. This time I decided to install Final Cut Pro X 10.3.4. Guess what? Runs smooth as butter just as it always has. All the angles, no proxy/optimized. Everything full rez running on dual 4k monitors. Runs absolutely perfect.
I then tested this on the iMac and got the same results. Runs perfectly.
I don’t know what it is, but FCPX 10.4 runs like complete garbage for me on two separate computers when “displaying angles” on multicam projects. Does this happen for everybody else when viewing angles on multicam projects? Very strange.