Bose,
While you are spot on about the examiner bits, I wonder about the flight with a PPL where the CFI refused to sign the licence because "the flight had to be with one of their Instructors to be valid"
If the flight was made in their school aircraft and you were not an instructor from that RTF / FTO then there may have been an insurance issue as most clubs prohibit training on their aircraft by instructors not authorosed by the CFI.
Regards,
DFC