Ha ha! Yes, that's what I used to see Forscan try 6 times but fail each time.
It kicked me out of the FDIM settings when it failed. Then I tried the FPV setting and it did the same. That was on my original unit. Then I tried on the SAT NAV unit and FPV enable worked, but still couldn't set the VIN.
These devices check the settings, it's not a forced write.
An example is when the error code comes back on the
CAN BUS for settings the VIN. Since setting the VIN is a multi packet CAN message, the error comes when it detects one of the VIN digits isn't "right". If you change the letters up front, you don't get to pass the rest of the packets because an error is returned early. If you change the last digit, the device accepts all packets up to that last one before giving you a response. The response seems to be error (in one packet) or success (seems to produce two packets).