Are the Era’s supposed to act as surrounds?

If so you should have added them to the Beam as surrounds. The sync problems you report make me think you’ve set the Era’s up as a separate room in the Sonos app which you then grouped with the Beam - grouped speakers will lag behind a soundbar when watching TV.

Split the Era’s if they are in one “room” in the app and add them as surrounds to the Beam.