Headphones wont play both channels

[Kirche3D]

Got a 2nd hand N95 8Gb a week ago, been working fine until yesterday music play back thru headphone only works on right side. The sound went muffled and dull, no sound at all from the left side.
Phone prompts correctly when jack inserted and equaliser settings still alter sound though with limited affect. Balance set to the just reduced volume in the right channel.
Ive seen some other posts, I tried the soft reset but it had no affect.

Then tried playback of video I had taken - sound was crisper but on Left only.
Now music plays only on left and the balance controls are reversed i.e moving slider to the left reduces the left channel volume.

Phone is on v 20.0.016

I'm assuming the answer is to re-install the firmware (which I'm not too sure about) However I'd like to know if anyone else had this or have any other ideas to fix ?
Is it common to have to resort to reloading firmware to fix stuff on N95's ?
Any feedback appreciated!

[Kirche3D]

Errm well, the more obvious solution of rattling the jack in & out of the scoket seems to have done the trick!