So, I was fighting a Hopper from the new spring event and after I won, it wouldn't leave the fighting screen! The only way I could leave the screen was by exiting and losing an energy point.

Here's a screenshot to show you what I mean:

http://24.media.tumblr.com/ce86483f2ea7ad6ab02fb000c1e9970b/tumblr_n1sxdiagvq1sw12vco1_1280.jpg

Now, I think the thing that may have screwed it up was the fact that I have a full inventory, since the hoppers drop leather. I'm trying to build a warehouse upgrade, but I'm missing a few items, so I was exploring and ran into this guy.

Thank you for reporting! We're working on this issue right now. Sorry for the inconvenience.

Update: the issue must be fixed now.