Didn’t we lose TWO shuttles to the loss of heat shielding due to the change in the composition of the glue?
No, the first shuttle was due booster O-rings that were too cold to work properly. Also, the joints did not have sufficient o-ring redundancy, which was changed after the accident.
No, we only lost two. The first was the contraction of the O-rings in the SRB segments due to cold weather. The rubber was too stiff and the hot gasses just blew right through the sidewall of the booster at the joint the O-rings were suppose to seal. NASA wanted a launch outside of the given safety parameters and the engineers refused. Eventually they were forced to sign off on it under duress, but got the head idiots to sign and letter agreeing Morton Thiokol engineers were absolved of any blame.
We lost the last one not so much because of the glue, but the foam insulation tiles that lined the main fuel module. It came off at just over mach 4 and the supposedly too-light foam that would not be a threat to the space shuttle itself put a 3-4” hole in the leading edge of her wing, which of course burned right through her during re-entry.