Thanks Rick, Yes, I did so today. Video Devices tech support recorded a clip in 1080pi59.94, to a Speed Drive and had no issue transferring it to a 2012 iMac running 10.13.6, and suggested trying another computer. I have a feeling my issue might be caused by having both 1080p29.97 and 1080i59.94 clips on the same Speed Drive, with the older progressive clips recorded first. I had intended on reformatting the drive, but in my haste, forgot to do so. Lesson learned here, always update firmware, and format drives first. Lesson learned— again!
Cheers