I'm also having this problem.
However before sending it in i tried metering exposure on a white A4 paper. when the EV is set to 0 (middle) the histogram shows peak to the left.
After comparing a few results i pushed the exposure to +1/2 and the peak is in the middle still shooting this white paper.
I suppose this corrects the under exposure problem without sending it to the service center.
Please correct me if i'm wrong.
However before sending it in i tried metering exposure on a white A4 paper. when the EV is set to 0 (middle) the histogram shows peak to the left.
After comparing a few results i pushed the exposure to +1/2 and the peak is in the middle still shooting this white paper.
I suppose this corrects the under exposure problem without sending it to the service center.
Please correct me if i'm wrong.