Spotify switches from streaming to bluetooth when phone is unlocked

[solarsd]

Plan

Premium

Country

Lithuania

Device

OnePlus A5010

Operating System

Android 9

My Question or Issue

Spotify is playing over a Bluetooth speaker and then I switch over to streaming to another device. Everything works fine and I put my phone down. If I unlock my phone while it is still connected to the Bluetooth speaker Spotify stops streaming and stars playing over the Bluetooth speaker. Spotify should continue playing over the device I selected.