Guild Wars 2

I completed Prized Possessions (HOTS) today but noticed that I seem to have been awarded too many mastery points.

While having completed two achievements which reward a mastery point each, I apparently have 4/5 mastery points.

Did I overlook something or is this a bug?

Update:

I played missions 9 and 10 of HOTS. Now the number of mastery points for chapter 2 is still at 4 and it seems I didn´t gain mastery points from mission 9 and 10 even though the achievments list a mastery point each.
However since I had two mastery points too much for chapter 2 due to a bug it seems now I am at the right count again.

For me the problem is resolved now, however it is unclear if it might occur again for other players or in future missions.

(PS:
I did gain some additional mastery points due to completing Insight achievements. )