Version: 1.16.5-0.3.0
Mekanism Version: 1.16.5-10.1.2.457

Not a super important bug but it is annoying.

When using this mod with Mekanism, the electric pump works but it leaves the water behind. So you are left with water in the hole and 1000mb of water in the pump, thus duplicating the water. This may be similar to #49 but they did not include any info and their link does not work so I don't know.

Interestingly this does not occur with lava. If you try to pump lava, everything works great and the lava block is consumed as normal.

Also one final note: Immersive engineering pumps do not pump water at all but they will pump lava. This may be caused by the same thing as the first bug but it may not, just wanted to mention it.

Apologies, the issue was a config setting with Mekanism.