I can't open the danknull with shift+rightclick nor by dropping it on the ground. I went to the control settings to hotkey "open nearest \dank\null" and assigned Lshift+rightclick to it. I was then able to access the danknull, but the UI had erratic behavior, making items disappear and others to duplicate and I just couldn't make it work (items won't stay in it). It even removes my armor??? FYI I'm playing with the direwolf20 1.12 modpack

Had the exact same issue, i just installed the latest version from here, don't forget to update the library as well found here