Upgrade bug in v3.-1.14
Due to a change in v3.-1.14 if either player cancels Wall Tower upgrade or they have not enough gold, Wall Tower 'memorizes' the type of the first clicked tower. When Wall Tower is finally upgraded, the tower of 'memorized' type will be created with correct stats and ability, but the model will depend on which tower player have chosen to upgrade.
This bug was fixed in v3.-1.15.