Linux (Manjaro) Why is there no sound when headphones are connected, but there is sound in the speakers?

Question

linux

The situation is this: A laptop, it has Win 8.1 and Manjaro 17.1 dual-boot installed on it,
everything is in order with sound in windows, when headphones are connected, the sound appears in the headphones.
When, as in Manjaro, if there is sound in the speakers, then when headphones are connected, they are silent.
If one nuance, manjaro is freshly installed, and the sound in the headphones worked on the first boot, it stopped after the reboot, i.e. settings are left untouched.
Everything is enabled in alsamixer, "Analog headphones" are enabled in pavucontrol and the slider jumps when music plays, but there is no sound in the headphones, just silence.
In general, the settings are fine, everything switches Speakers / Analog headphones, but there is simply no sound in the headphones ...
Linux kernel: 4.14 (tried other kernels, no sound)
Sound card: Realtek ALC668

Answer 1

I usually don't either when connected.
But then I do:

Open screenshots

After that, usually the sound in the headphones works for me.