I have had all sorts of issues with R22SP6 step - in/out. Fortunately we are migrating to R23SP4. Most of the failing files translated in this version with the exception of 1. That assembly file came in perfect to R24SP2.
I do not understand the different output speeds but the import could be slower if the optimization settings are different between seats.
Win XP64
21SP7/22SP5, 3DVIA Composer 2013X, ST R20
Dell T7400 16GB Ram
Quadro FX 4800 - 1.5GB