You can select the item to craft and set the quantity but are unable click the start button.

Just tried SSP and works like a champ the buttons and crafting so your correct it SMP only

yeah.,..i get what you are saying..this just isn't happening for me.. I don't know what else I can do

i will have to assume both of these issues are SMP? I'm having no problems in SSP

When I get to the modal where it shows all the items needed to do the craft, Cancel is the only button that works. I get the focus on the CPU and start buttons but when I click them nothing happens they don't even depress.

Also I have this problem on my server I did have this problem with the alpha on single player but will try it with the new beta

Works great in new version, thanks for getting this working in 1.12