I believe that I'm having some timing issues with my remote flash triggers...

The Gear:
Sony a500
Minolta 5200i flash
iShoot wireless trigger system (cheap ebay triggers that i hope aren't the problem...)

The Problem:
The top 15-20% of the frame is dark after exposures using flash with remote triggers.

My Hypothesis:
I'm guessing that the cause of this is that the shutter isn't completely open when the flash fires. I've tried exposures in every flash mode with the same results.

I'm not at all sure how to fix this issue or even exactly what is going on... any and all help would be very appreciated.

Thanks
Ben