Mission received for upgrading towers to Level 2 when already at Level 3
I just upgraded all 12 towers (the max you can have) on my Cobra base to level 3, which completed a mission. The next mission I expected to be was to upgrade/purchase guns at level 3, but instead I received a mission to buy a Level 2 tower. How am I supposed to purchase a level 2 tower when I have the maximum number of towers allowed. No, I'm not going to destroy a Level 3 tower to place a Level 2 tower for the mission.
I am assuming this is a glitch that needs to be corrected.