Run away memory leaks, beach balls, crashes

I imported my Aperture library into Capture One a long time ago. The result was a referenced C1 catalog. Over time I have been moving the images into a managed format. My catalog only has 22k images but it has many, many folders/albums. When I move the images from the referenced import to a managed album C1 starts eating memory. I don't know why. The beach ball spins and the hard drive grinds. The Activity Monitor shows C1 consuming a huge amount of memory. I took a screen shot showing C1 using 145 GB of space. Eventually the number will balloon to 260 GB before crashing. OS X says I ran out of memory. After crashing, it won't fire up again. It turns out some part of the application is still running but just not responding. I can't seem to find C1 in the Activity Monitor so I can't kill it. When I right click on the icon to Force Quit the application it refuses. Shutting down the computer properly doesn't work because OS X can't get C1 to quit. My only solution is to press and hold the power button.

Here's a JPG of the Activity Monitor reporting the 145 GB usage.

https://www.dropbox.com/s/7tdefmslsaapo ... y.jpg?dl=0

I'm repeating the experiment right now and I'm at 210+ GB. The system will crash again, I'm sure, and I will have to do another hard reboot.

https://www.dropbox.com/s/904ea40uk0zmx ... n.jpg?dl=0

Might as well... I'll use the time to make breakfast for my kids.

This doesn't happen with my "regular" catalogs that I am building up natively from scratch with new images.

Has anyone encountered this kind of behavior? Maybe you had a different stimulus to get this behavior?