had the same issue and used the "Reset-Procedure" to got it solved, but it came back and remembered that I setup a "Multiroom-Group" the day befor. I deleted this group and it works again. So, befor restetting the whole thing, try this.
Same problem here. I'm from Brazil. While using Alexa in Portuguese, all Spotify commands used to work well. Then, I changed Alexa to English and this problem started. Disconnect and connect the skill solved the issue, but only for a while.