My Fenix 5x Plus stopped syncing with Spotify at all. I have two problems and I am not sure if they are related to each other.
1) Connecting to WiFi
Adding a new WiFi shows weird behavior. I add them via Android App. The watch usually tells me, that the connection failed, however the App shows me that the connection was successful. This is inconsistent. Is this a known issue? Is Garmin working on a fix?
2) Syncing Spotify music (used to be fine)
Trying to update my library results in either an immediate failure or it starts to sync, but then after about 20% failes without proper error message (Sync failed). Subsequent attempts usually show similar behavior. On third or forth attempt I see the blue triangle and the watch soft reboots.... 
This is very annoying on such an expensive high end device. Not sure who to blame (garmin or spotify), but one of them should take the responsibility and fix this issues.
I tried several WiFis with and without WPA2 protection.
Edit:
Not sure if related, but it seems that the Spotify app behavior is inconsistent as well. Starting the App on the watch usually opens the menu with the volume bar and and play/pause button as well as a link to the library. However, sometimes it immediately shows my downloaded playlists, skipping this menu.