Pixel is clean, from a battery saver perspective, so that’s probably not your issue.

Not sure what to do next. I’ve used it for about 10 years now, and keep gobs of stuff in sync with it.

I do recommend Syncthing-Fork for Android, it moves the sync conditions into the individual since folders, so you get finer control.

Do you get any errors on the desktop console? On Android, if you launch the web client you get much more info and configuration capability (Menu - Web GUI). Once there, click the gear at the top right, and open Logs. Maybe there’s something there that can help.