If you expand a map twice, it will become invisible in the output slot of a crafting table, but you can still craft it.
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marcono1234
This is still a problem in 14w21b. Attaching video evidence.
This glitch is corrected by going in and out of the crafting table each time you expand the map.
15w43a
wobst.michael
Is this still an issue in the most recent versions (i.e. 1.10.2, or 16w42a) of Minecraft?
bemoty
Confirmed for 1.7.9 also gets name "unknown map"
Also shows scaled 1:2 Level 0/4 and after putting it in your inventory it shows: scaled 1:16 level 4/4
Man there are so many bugs with maps rightnow...
*Attached screenshot with "unknown map"