Playback takes about 20 seconds before it starts

[ManuelBu96]

First of all, thank you for the tool so that I can turn my Denon receiver into a Spotify player. Unfortunately, it sometimes takes longer than 20 seconds before the music starts playing. I can't quite understand why this is happening. The server on which the Docker container is running is practically not being used.

About the setup
Denon receiver connected via Ethernet
End device connected via 5GHz WiFi
SpotConnect in Docker provided by GioF71

This actually happens with all songs. What do you need to be able to help me with this?
When I start a playlist only the first song has this big lag.