Yes, it's barrel distortion. I tried correcting it in the Puggo Grande with a VirtualDub filter designed for that purpose, but the results were horrible. On some scenes it was ok, but on others it was completely unacceptable, such as on the crawl.
There isn't really a fix for it during capture. The WorkPrinter wasn't initially designed to capture the entire frame of a scope print, and with the enlarged gate you see it. Frankly, after being upscaled, I think it's pretty minor.
If you want something to play with, I think I still have a raw clip here: