Nokia 6 - couldn't update, verification problem, but updated anyway?

[Bartosz Skrzypczak]

Today I got an update to android 9 on my Nokia 6. The update appeared to go just fine and the phone booted into android 9, but after the update it said that it couldn't update due to verification problem. But I was running android 9 anyway. And after I clicked "try again", it told me the system is up to date.

Is there anything wrong or is that ok?

I also just noticed that something is wrong with sound. The volume keeps going up and down on its own (smoothly) every few seconds. This is a bit annoying when listening to music.
Edit: the volume issue was caused by dolby surround theatre mode that was enabled, while settings showed it was disabled. Enabling and disabling fixed it.