TL-MR3040 V 2.1 upgraded to 1.01

I have upgraded, but was unable to follow the recommended procedure.

My TL-MR3040 is version 2.1 and when I attempted a sysupgrade I just got an error message about image check failed.

But reflashing the V2 firmware with the old mtd-command worked fine. So now I have a working PB 1.01 on my TL-MR3040.

Is the new V2 firmware not expected to work on a V2.1 TL-MR3040?