Hmm, it's weird.
In your corrupted .dat, the last bump table value is missing and ending structure flag is corrupted.
But removing magic data from from corrupted file and inserting the .md3 gives a working .dat with a proper structure flag. Only the last bump table line (sector and value) are removed because afaik bump table couldn't have more than 14 lines... but everything's ok.
I don't know what happened. I guess there was already some magic data in your .dat before you imported the .md3 because in 1.912XE you can't insert magic data if no magic data is already present.
Maybe the past magic data was improperly overwritten... weird.