The dimensional crates are really glitchy as far as i have tested them in the FTB Unstable pack.
When placing them, it creates a lot of server side lag.
I don't exactly recall how but i have been able to duplicate items within the crates and the crates themselfs without too much hassle

What version of NeoTech are you using?

The one used in FTB Unstable 3.0.29, according to the modinfo it is 2.3.5

There have been a few reports of dupes with the crates, but I was never able to reproduce. Thanks to some users, it was found to be an issue of another mod (Dont know which one in particular, just from a list) This mod has since been updated.

Try updating to the latest unstable and see if that fixes it.