Begging the colonel’s pardon, it sounds like a people issue:  Don’t crank them up so loud?  (You can set a Room’s Volume Limit. using the Sonos app.)  The ES-500-AW-4 (note model# correction) could handle a power level of 120Watts RMS, w/ efficiency of 87dB, which isn’t super-loud but isn’t whispering either.  But a Connect:Amp had a maximum power output of 55 Watts/channel.  So the most likely case is that you drove the old Connect:Amp into clipping and that created waveforms that fried the tweeter.  But I’m just guessing.  If it’s the woofer that has had its coil blown or driver cone or surround ripped, it’s the speaker’s fault entirely.

I would attack it on both fronts: First, switch to new Amp’s, which have limiting circuitry to prevent frying the amp at least, and supply 125 Watts per channel.  Second, if you got the Episodes from a dealer/installer, complain to them because they put this stuff in without designing or configuring it.  Why do I say this?  If you need to turn up the speakers so loud that they blow up, then there are too few speakers installed for the outdoor space, or they should have installed a Connect plus a separate external amp.  But if you bought the Episode speakers yourself, well, good luck -- I would just throw them away.  But you can push on Snap A/V, which bought Episode and a bunch of other companies and seems intent on restricting distribution, despite what may have gone before, and pushing the “Recurring Monthly Revenue” model with PakEdge and Luxul etc.  They don’t deserve any charity or benefit of the doubt from you.  If it’s the woofers (see above), call it a warranty issue: sunlight, weather, power-handling, all conspire to make outdoor speakers troublesome, and they have plenty of margin to replace them.

[Edit: Oops, I made the rash assumption that you had only 2 speakers per Connect:Amp.  You said 6 failed, which I took to mean serial occurrences.  But… If you are running 4 speakers per amp, i.e. paralleling 2 pair, it makes the max. power consumption issue more acute.  To SnapAV’s credit, Episodes still have a Lifetime Warranty, but it’s “Limited” so they’ll probably make an argument for abuse given 6 failures, which is why I separated out woofer physical failure above as warrantied.]

With respect to not being able to be driven into “clipping” AMP and CONNECT:AMP share the same design criteria.

We humans have been conditioned to equate “loud” and “distorted”. We increase a system’s output level until we perceive some clipping distortion, then accept this as “loud”. Using this criteria a SONOS amplifier will likely never sound “loud”.  In my college apartment we could run the system to the point where verbal communication was very, very difficult, but the system sounded clean. Regardless, we would receive repeated requests yelled into our ear at close range: ”turn it up”. The same listening crew in another venue, playing an ugly sounding little compact system at distress levels, we never had a “turn it up” request because that system sounded “loud”. Conversation was easy.

That outdoor “room” is very large and a few small speakers will not sound very aggressive. Possibly adding a subwoofer will help increase the perceived loudness of the system.

My understanding as well. Plus the Connect Amp is not a high powered amp as such in the first place and a typical home speaker should be able to handle its power - unless left to run at 100% volume for a long time perhaps.

At what time intervals and in what sequence did the speakers blow? And under what playing conditions?

Waiting for the OP giving more data, but I’d like to know: (1) @buzz I recall a video produced by Sonos at the introduction of the new Amp where they specifically mentioned as new the auto-limiting and auto-shutdown circuitry in the new model.  Yes?  No?  (2) @Kumar It is specifically when an amplifier is underpowered and overdriven that the waveforms get distorted which increases the overall high-frequency content, which can burn out unprotected voice coils.  Yes?  No?  Class AB only?  ==Connect:Amp, or only older ZP120? (3) 6 failures, if in sequence, implies that the speaker wasn’t the problem, except for some kind of “bad batch” manufacturing issue.  Like to get your opinions regardless of that it doesn’t help the OP...

Connect Amp is also designed to not clip. In general though under and over powered amps can both blow speakers, but the underpowered ones do it sneakily. The over powered ones get the speakers to play loud enough for the sound to be painfully loud, and get turned down in time...usually! 

For external speakers driven by overpowered amps this may not be the case because sound levels get attenuated very rapidly out of doors, also given the tendency there for listening distances to be further away than indoors.

As far as the OP case is concerned there isn't enough information provided to help in a meaningful way.

When CONNECT:AMP or AMP is driven to the clip point, it’ll shut down. There may be some subtle differences in behavior as the clip point is approached, but the outcome is essentially the same. For mild transgressions, they’ll back off the Volume a bit. I think that the AMP literature was changed to emphasize the feature because there were some complaints about CONNECT:AMP and ZP120 shutting down.

If you gave me a job: “Please blow up this speaker”, a SONOS  amplifier of any generation would be my absolute last choice.

AMP handles low impedance dips more gracefully than the earlier models. Some speakers, while nominally 4-Ohms, might have a dip below 4-Ohms at some frequency. ZP120 and CONNECT:AMP would absolutely not forgive this and would immediately shut down.

In my college apartment we could run the system to the point where verbal communication was very, very difficult, but the system sounded clean. Regardless, we would receive repeated requests yelled into our ear at close range: ”turn it up”. The same listening crew in another venue, playing an ugly sounding little compact system at distress levels, we never had a “turn it up” request because that system sounded “loud”. Conversation was easy.