What the..? Trade-o-mats stopped working.

[Zuthilios]

Update: I just made a fresh clean server with only my map, so no plugins, settings or anything and trade-o-mats still refuse to work.

Firstly let me just say thank you to the community, I've had about 3 troubling issues in the past week and all were solved very quickly so thanks to you guys and keep it up!

Ok, so at first in server client 3.0.3 trade-o-mats didn't work. Then in 3.0.4 they started working again so I thought 'oh, awesome!' and built a huge trading area. Now after completing it they damn things have stopped working again!

I don't understand why this is happening, but between the two tests of them working and not working I have added some plug ins which may have caused them to stuff up (Core Protect, World Protect, World Edit, Voxel Sniper and Lag Meter). Otherwise I have no clue what I'm doing wrong. I also built exactly the same setups in a test world and they worked fine, so it must be something to do with my server.