In the party screen when you click on a troop type that is able to upgrade (troop [1]), and then drag the troop underneath them (which are not eligible to upgrade) to the top, and then click the upgrade button of troop [1], it says the troops are not eligible to upgrade.
(If you then re-select the troops (troop [1]) and try to upgrade them they are able to upgrade.)
Version E1.0.4
(If you then re-select the troops (troop [1]) and try to upgrade them they are able to upgrade.)
Version E1.0.4