This is a continuation on the thread
which has been closed for comments. Whence a new thread.
An update: I started to get drops from my Play 3 pair again tonight. .This means that the firmware update did not help. I have not noticed any of these drops in my Sonos Five pair yet. (Recall that I swapped rooms for these pairs, to test the hypothesis that the different usage profiles could matter.) This is promising.
Seems like I’m in for buying an ERA 300 pair, but it may take some time I come around to it. (It’s a bit of work to get them in place, since I want to mount them on the wall.)