I can't see the attachment. I also need to see if this version will help me. I have stuttering with Chromecasting. I've tried modifying and / or resetting all the settings in the Chromecast properties. I own 7 Google Home Minis, and am casting from a Pixel 2 XL. When casting to the "Everywhere" group, which includes all GHMs, I hear crackling and stuttering throughout the house (only one or two don't). If I listen where I can hear from multiple speakers, I can tell that where one speaker cuts out, another is playing that section. I know that your solution works differently to the built-in chromecast mirroring, but when I mirror through the Google Home app, there is no stuttering anywhere.
EDIT: I just tried beta 824 and enabled Chromecast alternative connection. Still stutters with the group (Even with buffer maxed).