Found this issue much to my dismay in PO3 Kappa mode had a multiblock Shelving Unit, filled to capacity with various items as you do.

Accidentally right clicked one of the blocks of the structure with a Cardboard Box from Mekanism and boy did this break things, initially tried unbinding the box to restore it, only succeeded in generating an invisible block (structure still not complete), I then tried replacing the block with it's equivelant (Iron Grating) but couldn't place anything because the block still technically existed.

I then had to break and replace this glitched block which brought back the structure but now all contents and chests had been lost for good, playthrough now ruined. Anyways enough about me, just reporting the issue for you guys.

It should be noted that this occurred on a server running Spongeforge 2838-7.1.8-RC3958.