[DAnconia55]

Or it could be a SYMPTOM of a problem induced by a meteor or foam impact on the TPS

Or it could just be nature throwing the dice and coming up you lose....

[TLBSHOW]

or it could be from the problems at NASA

STS 109 March 2002....Columbia suffers a systems failure during pre-test cycling prior to de-orbit burn.
Failure occurs in 4 port RCS thruster pack [pitch/yaw/roll]

[TigersEye]

Or it could just be nature throwing the dice and coming up you lose....

Or...it could be a natural phenomena that occurs during re-entry that has little or no effect on the shuttle and simply has never been observed before.