I've just had an experience that might have a bearing on your problem, or might not.
I was trying to programme a 14M2, in circuit, and had a sequence of verification errors, not something I've ever seen before. This was using the AXE027 cable, not your set up.
After a lot of head scratching I found the cause. This board has a couple of serial inputs from another unit connected to it, and has always worked faultlessly before. In this case I found that in taking the lid off to programme the unit I had accidentally dislodged the ground connection from the cable that feeds the serial data to this board. So, when I was trying to programme the board, pins C.3 and C.2 were receiving serial data from another unit, but with no ground connected. This caused the verification error, as presumably the differential voltages across C.2 and C.3 were enough to mess things up somehow.
It may have no bearing on your problem at all, but by posting in this thread it might well get spotted by someone with a similar problem in future, and save them half an hour of head scratching.