Somehow there are specific Prestige Achievements that stopped counting.
As you can see in the screenshot, I have 100% of continent Zandorya completed, however the continent achievements all stopped counting at some point.
All zones are completed 100%. And I tracked all boss kills and elites.
They counted in the respective zone, but they did not count for continent.
No matter if I kill instanced bosses/elites/mobs at all, they count in the zone only, not for continent.
In the beginning of the season they counted correctly. but I don't know when they stopped...
Please check this.
As all the zones are completed already, how could I possibly complete the continent ? No additional kill would count right.

I think this affects all "continent" achievements. In Balanzasar I just tried a Boss and this also only counted in zone, not for continent.