When the player is wearing armour (so the armour bar appears), the armour bar may obscure the bottom of a held map, making it difficult to use.

Occurs with default window and GUI size.
Does not occur (workarounds):

• Set to fullscreen (on my computer at least, resolution 1440x900)
• Set GUI size to a smaller size than it would be if set to auto
• Make window taller than it is wide (although that's ugly)

Sorry in advance if this is a dupe, I searched and didn't find any previous reports of this.