I've started noticing that when I click between Tool Tab Menus, I sometimes get the Rainbow-Spinning Wheel, which hangs for a moment or two, before finally switching to the chosen menu. The program never really comes to a full stop/crash, and I'm more describing a bit of lag here - just an annoyance that seems to slow me down from time to time. It's not a major problem, but when you're trying to tech whilst under the pump - jumping from changing Capture Folder, to checking focus, to adjusting colour, and back again in literally seconds - the lag makes me feel a bit off the ball.
Now I can't seem to replicate the problem, so I'm having trouble isolating it— but I don't suspect that it is a computer ability thing as I run a pretty new & up to date set up, and have noticed it as well on other photographer's machines. I use a for-shoots-only MacBook, with a virtually empty SSD (453GBs free of 500GB). I close all unnecessary programs, widgets, background apps etc while shooting.
It's not happening right now: testing with an empty session with no pictures, and no camera tethered. But it did occur today tethering a Canon 5mkiii, in a session with <1000 frames. It didn't happen the other day working with bigger Nikon 810 files, in a much bigger session. Has happened with both 2nd monitors, and no external monitors running. The only other thing I can think of is in some instances like today (in studio), I kept a Lacie Rugged SSD also plugged in all day doing auto-backups through ChronoSync while we worked.

Has anyone else noticed this in their workflows?
My problem setup:
2015 15" retina MacBook Pro , 2.5GH i7, 16GB RAM, AMD Radeon R9 Graphics, 500GB SSD
OSX Yosemite 10.10.5
Capture One 8.3.3.23 (ace 7587) - OpenCL on Auto