My Jolla 1 seems to have gone numb.
No incoming call alerts, and even worrying, no wake up alarms.

It went shortly silent in the middle of some music playback, came back for a minute, and then silent since.

I guess this is sadly some hw related issue, still, Any ideas how to check if there is some sw related cause?

It is a hardware-related issue as the contact pins of the speaker got weak contact to the board. But it is easy to fix if you have a Torx screw driver.

Open the case in the lower part, locate the speaker block and carefully bend the contact pins upwards a fraction of a mm. Don't overdo it, though.

After that the speaker should work like new again.

Thanks, it worked.
I never disassembled my Jolla before, so I had a bit trouble in removing the upper part of the frame. Some hints for others:

• At the end I used an old credit card on the right top side to apply more force(opposite to the buttons).
• iFixit has a quite decent teardown with pics: https://www.ifixit.com/Device/Jolla
• And as mentioned in above link as well, you will need torx T5 (I was stuck first with a T6 I falsely borrowed from a friend first But if you do first, and think after,.... )

If you have any sound issues with Jolla 1, while you are at it, replace original speakers with those suggested here: https://together.jolla.com/question/...comment=145763

I used the suggested Nokia Lumia 720 earpiece and HTC One X (S720e/G23) speaker (not earpiece). It was worth the upgrade, because with the original part, there was a crackling sound in the earpiece at loud volumes. It went away completely, and the loudspeaker sounds better, too. This was 1,5 years ago, still works fine.

So after half a year of working unproblematic, loudspeaker contact problem is back again. I'll probably have to buy a torx set as my colleague who borowed last time moved abroad.

I bought mine in Maplin. Worth a try if you live in the UK. £1 for this thing (only one, not all 4 ):