The Core samples say different things for different players.

[SirMrSheep]

Hello! My mod version is 1.16.3 for both immersive engineering and immersive petroleum, as well as, the Minecraft version. I play on a server with close friends with about 30 mods and we've noticed that the core samples say different things for different people, for example, for me it says there is not a fluid reservoir but for others there is. I then go and make a pumpjack on it and there is oil indeed.

[TwistedGate]

Sounds like #181 to me, which should've been fixed in 3.1.0-2