@applee thanks for the reply. Good to hear.
I bought my (refurbished) N5 a few weeks ago and I am still figuring out, which bugs are "normal" or seen before.
So far, I turned it off a few times, cleaned the plug, plugged the headphones in and out several times*, but it didn't affect the issue. I was outside in the cold for some hours when the problem occured. Now in my warm room, it suddenly works again. Maybe it's simply temperature -> contraction/expansion of materials... I try to reproduce it in the next days. However, from now on I will always take my headphones with me. And, I guess I'll just buy me a Volla-Phone...
Best regards
*did you know, that the volume gets turned a bit louder everytime the headphones are plugged in? It got really loud after some switches 😲