Hagen Elite Mini filter issue: ait tube filling with water

[TigerRegalia]

Hi all,
I recently moved my betta into a 5-gallon (cycled) tank, and I am using the Hagen Elite Mini filter in it (it works great with a 5-gallon tank). Everything has been fine up until recently- I started hearing water dripping from somewhere, which led to my discovery that the air tube on the filter is filled with water and dripping, causing the water level in the tank to drop significantly over time.

Here is a picture of the airtube filling with water (you can see the water line about halfway up the tube). I apologize that the photo is not right-side-up; I could not fix it.

Anyone know what is going on with this, how to fix it, and/or if it is affecting the filter's ability to filter the water effectively?