See the second part of my comment. In addition to the Cambodian DCA, EASA
did single out
Siem Reap, but did not provide any details for their action. This is not the same as the blanket ban for carriers from the African countries and Indonesia (see the same link), which would be the case if the ban was completely based on DCA shortcomings.
Given their close association with PG, I admit I was surprised by the ban. I cannot explain the decision, but it leaves some unanswered questions on the table.