Fluid resistance turbo trainer – sloshing?

I just bought a used Elite Muin Smart b+, and when I turn the spindle by hand it sloshes. Surely the chamber should be full to the brim of fluid? Anyone know what kind of oil is in it? Mineral or silicone?

I found this blog:

https://www.merlincycles.com/blog/elite-muin-smart-b-trainer/

with this comment:

The first neat, built-in feature I noticed on the Muin was the initial sound of the fluid sloshing around. The sound acted as a reminder to go the toilet before settling in for my first proper ride.

so it sounds like that is normal.

Hah. Thanks.

When riding it makes a bit o regular sound like something’s rubbing. Kind of a shame because it’d be almost silent otherwise, but it’s not too bad.