The first two crashes were while trying to put Orange Obsidian Shulker Boxes in an RFTools Modular Storage. However, I was informed there was a tool tip identifying the crash so I tried to verify but crashed a third time while just hovering my cursor over the shulker boxes. As additional information I have named the two orange obsidian shulker boxes "~ SpeedSlider ~" (without spaces) since I am playing on a private server and in case I forgot to pick them up.

https://gist.github.com/SpeedSlider/b6028baf83d7fea62255a047768a4262

Already fixed in dev.