Sound reduced when locking phone and starts texting

[YMNemesis]

So, since the latest update of the Android (or spotify), whenever I lock my phone, the sound is reduced for 3 seconds and then comes back. Same thing happens if I start to write something on the phone (Even search for a song on Spotify) or just plain texting.

I have no idea how to disable this and why it even started? Some developer must have noticed and thought "Hmm, this isnt smart" but after two weeks, **bleep** is the same.

Hope you clever boys (I assumed the gender) have an answer for me!

Info:
- Happens every time my keyboard is brough up on the screen

- I have a OnePlus 3

- Android 8.0.0

- Spotify is up to date, so is phone

- Happens whether the phone is on do not disturb, normal or soundless.

Please lads, I am getting insane!