Video Enhance v2.6.4

Nope.
It turned out to be the default Slomo setting of NaN and manually setting this to 100% started things off. I had previously ignored this as I stupidly assumed it meant ‘Not Applicable’.

However, I now have a more serious problem that makes no sense - the converted files are running too fast! If I go from the source at 2:00:59:12 and run it to 24fps in Cronos, it end up 18 seconds too short compared to the original file, and if I run it to 23.976fps it ends up 8 seconds too short.
Why is this happening - and more importantly how do I stop it & get an output file the same length as the source file was?