Just from the perspective of technical feasibility, with no real theory (new or proposed) resulting:
a) pilot (or someone) pre-programs left-turn VAMPI before IGARI is reached. This is before 1:07 and so appears as an ACARS event
b) ACARS off or gone, no more events logged and reported
c) pilot (or someone) programs or turns 40 degree course correction for reasons unknown, but could be to lessen suspicion of Vietnam ATC. No ACARS so no record of this
d) as soon as 40 degree turn is achieved, then left 180 degrees to VAMPI, no ACARS now so no report of this...
with some "mastermind bizarre logic" ascribed to this sequence of events, it would at least "explain" what barrel_owl or others are questioning?