Headphones make Nokia act weird

[throwaway890]

So I've had this Nokia 6 for almost 3 years now, and in recent months I've been experiencing weird behaviour from it. Whenever I plug headphones in, the phone starts acting up. This includes:
1. Volume turning up and down by itself
2. Google assistant being randomly alerted
3. Being unable to turn the phone off
4. Random pausing of the song I'm listening to
These effects stop as soon as the headphones are removed, and can either start as soon as the headphones are plugged in, or a while after they're plugged in. I know it isn't the headphones because I've tried multiple pairs of headphones on the phone and the same effects occur.
Is there any way I can fix this?

 

[MoodyBlues]

These effects stop as soon as the headphones are removed
...
I know it isn't the headphones because I've tried multiple pairs of headphones on the phone and the same effects occur.

I hate to be the bearer of bad news, but this strongly points to a hardware failure. I think your only choice is to have the device checked by a reputable repair shop/person, but given the COVID-19 pandemic, I don't know how easily that can be accomplished.

Or buy a new one!

 

[Hadron]

The first, second and fourth of those could be due to a bad connection in the headphone jack. Number 3 is weird.