Invalid ECU image

in V-MAX
After flashing Yamaha VMAX ECU 2S3-8591A-30 (EU) using Stock ECU.ftm the flash was ok, after changing some ECU setting it would not rewrite the changes keeps coming up invalid ECU image, i then Flash the ECU in unrestricted .ftm and had the same problem. I purchased a new license and after only 2 rewrites stop working and is now asking me to purchase another new license, has anybody else experienced this problem.
Regards,
Kev.