Hi guys
Well after passing T/D and starting the descent, I went on Youtube to watch a video, after several minutes I noticed that VNAV was disengaged and A/T was on ARM mode on the FMA. if i recall correclty, the only way to get back to VNAV was to engage N1 mode or V/S and then press VNAV again to work. A friend had the same issue.
As i wasn't there when the bug appeared, I need people to confirm if they had this odd behaviour.