Stitch count was off by 1. (End is 1 command not 2 bytes).
Hoop used calculator was bad.
Timestamp was static.
Pure Janome jump sequences are Non-Full-Jump and perform the math as with one jump coord always going full distance on some parameter rather than evening the jumps out.
inkstitch/inkstitch#231 contains reports that some Janome Software produces failures to load issues.