I found several posts related to this, but no answers how to make it work.

I have a solution that I would like to share:

Problem

Alexa routine will stop if Alexa is asked to say something (Good Morning phrase, flash briefing, weather, etc.). This only happens when running a routine on a SONOS (or any other non-Amazon) speaker. 

Solution

As a work around you can use and IFTTT trigger to run another routine in parallel. To stop things happening at the same time, you can add a time delay to your original routine. See examples below of how this works pragmatically.

The solution is a workaround, not an ideal solution. However, I would rather have a higgldy piggldy workaround rather than the function no longer working as I want better audio than an Echo!

Before:- Routine would stop after bracketed action

Workaround:- Subroutine is run and delay is added

IFTTT Subroutine:-