No, I'm running the Merlin releases in this beta stream, (started with the alpha, as it arrived just the day before I received my shiny new tri-band WiFi 6 router!), but I found this as a known issue on stock firmware as well. See...
Does this include updates for addons in general on AX11000 (and presumably other HND routers) where the /opt partition isn't mounted R/W at boot time?
In particular, I want my swapfile and Entware and other addons on a USB drive, which requires re-mounting /opt to /tmp/opt at just the right...
I solved all my Sonos issues on any release (beta/production/alpha) merely by setting the 2.4 GHz radio bandwidth to 20 MHz only, not 20/40 MHz auto/co-existence, which is the default setting on ASUSWRT. The 40 MHz channel width theoretically increases the available bandwidth in 802.11n (now...
The better practice would be to run regular backups of jffs to a USB drive. Install NSRU from AMTM and either take a new backup manually whenever you make a change, or set up a cron job to run backups daily/weekly/monthly/whenever.