Im doing a simple sim of a cup with fluid inside gets thrown onto a surface. I've imported my model, fractured it then glued the pieces together. Next I made a sphere and clicked FLIP fluid from Object. When I sim, the fluid basically passes through the mesh.

I've made sure the collision volume is right, but I'm basically stuck here. Is there a way to make it take more time to check if the particles are passing through the collision volume? Do I need to make a thicker proxy?

Here is an example of what is happening: https://streamable.com/6kovu [streamable.com]

You might need to increase substeps in the flip solver. It also looks like your fluid is pretty low res and doesn't initially fill the cup. It might be difficult to match the movement of the cup this way.

Have you checked the collision guide under the flipobject node? That gives you the correct representation of the collision object.