I have experienced this bug as well. These kennels have been "building" for approximately 75 turns. Due to the negative combat speed implications of full plate armour, this makes heavy units (with the ability to move and fight) impossible to train.

Notem Batem: It is a common misconception that plate armour was cumbersome. Note this excerpt from Wikipedia on full plate armour.

"While it looks heavy, a full plate armour set could be as light as only 20 kg (45 pounds) if well made of tempered steel.^[2] This is less than the weight of modern combat gear of an infantry soldier (usually 25 to 35 kg), and the weight is more evenly distributed."