I have just downloaded the game and startet it with tutorial on. At lvl 11 I had to stop and do something else so I returned to main menu and closed the app. About an hour later I opened the app again and loaded my old game. When the loading was done I could only scroll over the "map" but could not activate any buttons (like none at all: buiding a new tower, open the menu, ...).
So then I opened the games pause menu by pressing the back button of android and restartet the game and it was all touchable again.
Same thing happened in this game again when I was at about lvl 33 and wanted to test if the bug is reproduceable. So I returned to main menu and - without even closing the app - loaded my game again. Well, the bug is reproduceable...
I really love the game so far (played it in w3 a lot) but the function to "save" and "load" a game is so important for me, for me playing it when I have to wait a little for something.