Hi mangotam I have got the same issue, and it seems like it only started happening since some time in September. Just wondering, did you get any feedback after you submitted your ticket?
It's really annoying when the first second or actually almost first 2 seconds are being dropped. It kinda feels like it's trying to do a fade-in. It only seems to happen when you select a song to play or when you skip the current song and go to the next song. If you would just let it play and automatically go the next song then it seems not to happen. I also figured it only happens with SpotifyConnect. If you use Spotify to connect to the WiiM Pro via Chromecast then this problem does not occur.