Copper Flute Glitch
 

When I equipped copper flute, I noticed the face indicating morale improve for my Dwarf Engineer units (as it should). However, when I unequipped the flute and re-equipped it, their morale stayed neutral.

The copper flute only worked the first time I equipped it and did not work after that, so I destroyed it for the mana crystals. Please fix this in the next patch.

Have you tried changing the slot of the dwarven unit? Sometimes it helps :)