When attempting to craft the obsidian ring using an obsidian skull and a firecharge in an anvil, the GUI shows the obsidian ring in the output slot with a red zero over it, leading me to believe that it's trying to craft zero obsidian rings, leading to problems. Clicking on the ring causes the GUI to update, showing a red X over the "produces" arrow and no product in the output slot.

We have baubles installed on the server, I had plenty of levels to craft the item, and no error was produced in console on attempting to craft this item.

The issue has since been fixed, and we have no idea what fixed it, because neither baubles nor Random Things were updated.

Weird^^.

I just tried it and it seems to work fine, do you have the same version of baubles installed on the server and the client?

This problem has just started for us, Sky Factory 3 server. What's different is that I have successfully made two obsidian rings before the bug.

A little more detail: made one about a week ago. Having proven its use, decided to make three more yesterday. I made three obsidian skulls and a lot of fire charges, then went to the anvil. It broke immediately after the first obsidian ring was made. I tried changing names, using other charge, the other skull, getting extra XP levels, restarting my client- though admittedly I have not yet asked for the server to be restarted.

Picture included. In it you can see I have enough levels, also left F3 on by complete accident. Any attempt to make the '0 obsidian rings' will result in the arrow being covered in a red 'X', as minecraft typically does if there is no result in the 'anvilling'.

Anything else I can do to find the source of this error?

Didn't expect to get ahold of the server admin for a restart so quickly. About half an hour later, we restarted the server. Went to check and it worked, picture shows both I made (forgot to get an inbetween picture of the anvil working). Seems like a server restart cures this odd bug.