The FM radio in my phone uses the earphone cable as the antenna. It plays the music just fine if I plug the jack in about 2/3 the way (and only hisses without it). But if I push the jack all the way in, the phone starts outputting all the audio to the earphones and mutes the speaker. The range between "antenna OK" and "Earphones active" is about 2-3mm, and the jack is sitting completely loose, so I can't even move the phone or either the jack goes loose or the phones activate and mute the speaker.
The phone is Xiaomi Redmi Note 2, running Android 5.0.2 if that helps.
[actually, I don't really care if the earphones are still active; I just need the speaker to work]