Router can only grab fluid in first fluid slot

[geradeaus007]

Describe the bug

When a router tries to move a fluid from a block into the router it will not work if any other fluid in a slot before it is present.

How to reproduce the bug

1. Set up new 1.20.1 instance with Forge, JEI, Modular Routers and GTCEu Modern (where I encountered the bug).
2. Load up a creative superflat world
3. Place down any buffer (Basic, Advanced, Advanced II)
4. Fill the top most fluid slot with water and any below with lava

5. Place router with a Fluid Module Mk2 and filter (whitelist) it for lava to tranfer into the router.
6. Place Bucket in router
7. Witness nothing
8. Invert (Blacklist) filter and witness water
9. Place a new Bucket and Invert again to witness lava

Expected behavior

The router should be able to grab the filtered fluid from any slot, regardless of any other fluids present in any other slots.

Additional details

Encountered on Star Technology modpack with the GregTech Electrolyzer with Water and filter for Oxygen (always 2nd slot).

I couldn't think of another mod with multiple slot tanks, so might just be a GT compat issue.

Which Minecraft version are you using?

1.20.1

Crash log

No response