Archos 50 Platinum Headphones attached error

hi guys

my friend has Archos 50 Platinum running android (no idea which one)

and he has that symbol for headphones even there are no attached which means i can't call him becouse he won't hear me (if he attaches headphones or spkr. he can hear me thru that)

we cracked it open (teardown with really bad photos is on the go!) and i can't find anything no board damage anything looks clean (he's glas is broken) we checked really good on that 3.5mm jack and there is nothing i did use antistatic brush(on whole board + 3.5mm jack) and nothing comes out (it's clean) he also used powerful compressed air at he's school still nothing

any ideas ? i can't reset he's phone to factory state (or root it)

rebooting dosen't help(we didn't crack it open while it was working...)

could be this a software issue ? why?

maybe just smth inside 3.5mm jack bendt or so? (if that 3.5mm jack is broken we won't replace it )

i didn't messure that one since my multimeter is cheap of $@$* and i have no idea which pins... there are like 6 or more i think ?

let me know what you come up with!