I just updated my client(1.12.2) and server(14.23.4.2479) to the latest quark(1.5-126) and autoreglib (1.3-19) and when I logged in and opened my refined storage grid inventory I crashed out of the client.

crashlog: https://gist.github.com/xannor/25fa8f9905239cfca6448c41361153d4

Edit: looks like I should have posted this to the arl repo instead of quark.
Edit: looks like refined storage has nothing to do with it, got same crash just opening the inventory.

The inventory crashlog was identical (Except for the timestamps). I also created a single player creative workd and as soon as I put a modular storage block from rftools into my inventory I crashed out, again with the same crashlog.

I have not tried it with any mekanism items (I have tha mot as well) but it looks like #955 is the same issue. I looked at the code line where the log reports and, though I do not know much about forge's capability system, I think the assumption of the capability being present and that the interface is also present is the problem. I don't know if the capability wrappers, in rftools and mekanism, report true for all capabilities, or if somehow the DROP_IN_CAPABILITY is getting assigned to the wrappers.

Edit: I just tried it in the single player putting a mekanism machine in my inventory so I can confirm that #955 is the same issue as this one, crashed out with the same crashlog.

Edit: I can also confirm that backing down to Quark 1.4-125 and ARL 1.3-18 does not exhibit the issue in single player, don't want to try to back down the server yet.

Same bug as VazkiiMods/AutoRegLib#13

Just wanted to confirm that with ARL 1.3-20, I do not crash in the single player, going to update my server and verify everything is good connecting to it as well.

Edit: Yep, server is good to, so all fixed! Thanks!

What is the crashlog when it is your inventory.
Edit: Does this happen in a single-player word?