volume lagging when using radio

rpi 2b, volumio 1.55, hifiberry dac+

I have added some local radio stations to the the radio list. It works well, but the volume is lagging for approximately 1 min. The volume knob is responsive, but the actually volume does not change. After a minute or so it stabilises and volume knob and actual volume are in sync.

Any ideas what might be causing this behaviour?

Example of a pls file for a local radio station
Title1=Sveriges Radio