I have a strange problem. It just happen recently, when I accidentally unplug my headphone. But I unplugged it before and nothing happen. Basically now, when I use my headphone through front jack, when playing videos, I can't hear voice. Only background music. Using kde sound setup, pressing front left and front right test button, result in a mono sound. No distinction between right and left. This only happen with front jack. Rear jack is working fine.
For me, I also had this problem when using my Apple 3.5mm headphone on Kubuntu, but when I held the volume up or down button, it had no effect on the actual volume, but my headphone had a sound.
To solve this problem, simply pull the plug a little and the sound will recover.
Probably because the top connector is for controlling audio input, but the input and output on the motherboard are separate, so you can't insert the wrong interface if you want to use the output function normally. Of course, the input function is not available when the output function is used normally.
Forgive me for my poor English, good luck