Hi Andrew
You hit the nail on the head. Egyptians can't pronounce the sounds 'p' and 'v'. That is a reason why the pronunciation of the loan words is mutilated compared to the original Greek.
Mostly all words of Greek origin where the ⲭ is followed by ⲏ, ⲓ, ⲩ, or ⲉ it is pronounced /sh/, again a rule that I find rigid and meaningless to some extent, as in /abarka/ and /awka/. The examples are: ⲭⲉⲣⲉⲧⲓⲥⲙⲟⲥ, ⲁⲣⲭⲏⲉⲣⲉⲩⲥ, ⲓⲥⲭⲩⲣⲟⲥ, ⲯⲩⲭⲏ, ⲭⲏⲣⲁ.
Ⲟⲩϫⲁⲓ ϧⲉⲛ Ⲡ̀ϭⲥ