Without seeing the code, it's impossible to say what's going on, but here's a few things.
1) Setting the scale to -1 doesn't work properly in all version of Mach3 even without comp. Only in the last year has this been fixed to work without comp.
2) From the looks of your toolpath, I'd say that you have duplicate lines of code at your transition points, or very, very small segments at those points that are messing up the comp. I saw this the other day, and it was due to bad g-code, and not comp's fault.