I have noticed that there is a flaw with the Crafter that introduces a BC break.
I came to this conclusion whilst watching this video: Knarfy showing Wool recipe in a Crafter

For example, if you have a crafter set up like this:
S S X
S S X
X X X
where S = String, X = disabled slot

it will currently craft wool blocks when spammed with a Redstone signal, since there are at the moment no recipes for any combination of the inputs.

If Mojang were to add, i.e. ropes with the following (shaped/shapeless) recipe:
S S X
X X X
X X X
any contraption using the previously mentioned setup will suddenly craft ropes instead of wool.

My proposed idea for avoiding this is:

• Check for toggled slots
• If there are any toggled slots, only match shaped recipes that match that shape

The upside of this change is that it not only fixes possible BC breaks, but also it essentially doesn't change the functionality of the Crafter in a gameplay affecting way, whilst future-proofing any automated crafting.