I have never heard before that bytes in a flash may be mixed via dropping to a floor

Jokes apart, what may have happened is that one of the tiny wires that connect the silicon die to the chip pins may have snapped when the chip was dropped.

But still there is one confusion - from the posts I got an impression that many MCUs had failed.
Stanley had written Everytime I put the motors near the MPU, the MPU failed.

Maybe all of them were dropped before using.

Raghu