Fluid Vessels not coupling together?

[six-shooter]

Heya, I have the issue that fluid vessels don't connect to eachother anymore to make one big one.

Normally I placed them in a 3x3 shape next to eachother, and they would fuse together. When placing one vessel on top of that, it would create another (3x3) level on top of it.

This doesn't seem to work anymore?

Halp?

[hlysine]

Please attach some screenshots of how it isn't working.