There are a few companies where I'll get a 8/10 with no explanation. To me, that's a low score, if there's no explanation provided. I pride myself on my 10/10s.
I've only had one shop rejected, and at first, it was seriously for no reason. I followed the guidelines exactly, and wrote up my report exactly as events happened. My report made it through initial editing and receipt verification, but got denied at the final step. This was a MSP that runs your reports by the client for final verification/approval, before your check is cut. This was a two-part shop, and my report got denied because my report on Part One was awful. The client didn't want to believe one of their employees would go so far against company policy to cut corners, and use foul language on top of that. My shop was denied because they basically said "There's no way things happened that way."
After I disputed the shop rejection, the client, to their credit, suspended my rejection and requested a Part One (phone shop) to be performed by another shopper, on the same location, same employee, using the same information I gave, and.... the employee cut the same corners again. They couldn't dispute it that time. I ended up receiving a double shop fee for the hassle, delayed pay, and verbal abuse I received at the hands of the employee.
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Plan the work. Work the plan.