I have actually found 4 beetles. 2 in oasis, and 2 on krokosphinx island.
Visually, it looks like there are four beetles there, but you do technically "zone" away from the Oasis when you get on the boat and when you go through the oblisek portal. Also, those two other beetles are not labeled Oasis either.
There is only one beetle on Krokosphinx island. The other one is on the Tomb of Storms island.