I'm having the same issue with GrooveIP on the slider. When I call someone it rings in the earpiece, then when it connects the phone switches to speakerphone and I have to press the speakerphone button twice to get the call to the earpiece. When I answer a call from someone the sound comes out of the earpiece by default as it should.
I had a similar problem with Skype as well. The version before it updated earlier this month (my version is 2.6.0.95) I had the same problem where calls would start in speakerphone and I had to press the speakerphone button twice to get the sound in the earpiece. After it updated to 2.6.0.95, all calls were in speakerphone, and I cannot get it to go through the earpiece. Pushing the speakerphone button doesn't do anything besides make the audio skip as if it were trying to switch between earpiece and speakerphone, then return to making sound through the speakerphone.
I am also using the stock version