What version are you playing?
Similar thing happened to me on 0.5, the monster's arms and body was on top of each other( Couldnt click at his arms multiple times, took me 5~7 mins to kill it lol)
Fixed in 0.7.
0.5c, but exiting and reentering the game fixed it. Had it happen a few other times on other normal encounters, same thing fixed it.
We fixed this issue in version 0.7. There is an improved version for android.
