rapid decompression?
I would speculate that decompression issue in the climb (with crew incapacitated) is inconsistent with the A/C going into descent shortly after reaching CRZ ALT.
It would have stayed in CRZ ALT or selected ALT until out of fuel if I am not mistaken (see Helios).
Somewhere in the press it mentioned that A/C had come out of maintenance on Monday. If this is not significant then it might at least be noteworthy.
FL380 is pretty close to FL390 which is the standard max. service ceiling for A320. What's the UTC? A few seconds?