The fluids should collide with standard Unity colliders (so far, I'd like to change that at some point). Only then the cumstains are attached to the "closest" skin point, which does not always work very well for mouth/tongue. But they should not fall through like this.
Do you have all colliders enabled normally, no weird ColliderEditor changes?
Or did you maybe tweak the "Do not Collide Near Emitter" Advanced setting? It exists there to prevent collisions with the emitter (especially important for squirt). Maybe the tongue/mouth is still ignored by this setting, try reducing the value for the penis emitter. Although now I see in the vid the Advanced tab appears briefly and it's set to 0.5cm, so that should be fine. Maybe try setting it zero to check if there might be a bug with that logic. Iit's kinda hacky since you really can't run on/off collisions of individual Unity particles, which is why I ultimately want to write my own more fluid-like sim instead of partially using Unity's particle system. But that won't happen this year.
And if that does not help, can you share the scene with me to test what's happening?
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