Virb Edit Mac 5.2.1 doesn't stitch import from HDD

Hi:

I just recorded a 90 minute concert in 5k RAW. I would have loved to do it in 5.7 but the camera shuts down after 20 minutes, so that's useless. Anyway, apparently the only way to get an option to stitch is if I import all 67 GB from the camera - which causes Virb Edit to hang 4/5ths of the way through, after many hours. If I copy the entire disk image to an external drive, I can import and optimize the clips - but not stitch them. The option is never available. If I bring the clips into into Make Video, it doesn't recognize them as 360. This makes the software completely useless. I am on a new iMac Pro (2017) 3.2 GHz, with 32MB RAM and a Radeon Pro Vega 56 with 8GB, running High Sierra 10.13.2. Any help appreciated.