This was probably one of the last transmissions of the satellite before re-enters. At that stage the orbit of the satellite changes a lot and the TLE we get from our external sources, mainly space-track.org, are accurate only of a couple of minuter to couple of hours. So, the shift you observe is a result of non-accurate which results in wrong Doppler calculations.
In the past we have followed some missions before re-entry and generated our TLE sets based on our observations with pretty successful results. Check for example the Bobcat-1 story in NG-14/ELaNa 31 Launch and Deployment Information - #96 by Kevin or RamSat one in RamSat mission progress - #152 by pethornton.