Android app constantly freezes / crashes with update 9.0.1 update.

True, but mine is failing in a similar way even though I am only playing to a single device... It is comparatively rare that I have more than one device playing at a time.
I'd try and restore the system to its supported state; enable at least the wireless cards again, this might solve the issue.
Over the last 7 years I've tried all of the setups, and none comes close to wired+EoP - so I've no intention of changing it - particularly as those similarly affected seem to be using standard setups and it makes no difference.

A wired setup is okay, and I don't have experience with EoP (it may affect the system similar to Repeaters/Wireless Extenders), but disabling the wireless card(s) can cause strange happenings. Enable the wireless cards again, temporarily, just to exclude the disabled wireless as the cause of the issue.

A wired setup is okay, and I don't have experience with EoP (it may affect the system similar to Repeaters/Wireless Extenders), but disabling the wireless card(s) can cause strange happenings. Enable the wireless cards again, temporarily, just to exclude the disabled wireless as the cause of the issue.
When I still had the wireless enabled, the Sonos devices seemed very flaky over which connection method to use. Even though they were wired, sometimes they still chose to use Sonosnet. It drove me mad when trying to pin down the intermittent problem that I had, so I disabled the wireless - and the system has been considerably more reliable than at any time in it's seven year use. Consequently, although this particular controller issue is a bit irritating, I put a higher importance on reliable streaming :-)
I do, of course, accept that the majority of issues raised here may well be networking related, which is why most of my permanent devices (particularly anything Sonos related) has reserved addresses. However, I'm really not convinced that every problem encountered with the software is network related.

[...] However, I'm really not convinced that every problem encountered with the software is network related.
There isn't a known bug related to the Controller app either.

[...] However, I'm really not convinced that every problem encountered with the software is network related.
There isn't a known bug related to the Controller app either.

Are you part of the development team for Sonos? If not then I don’t see how you can confidently say that. If so then I apologise and accept your word 🙂 It still doesn’t mean there isn’t a bug though!

It still doesn’t mean there isn’t a bug though!
Why would Sonos not acknowledge and admit a bug?

It still doesn’t mean there isn’t a bug though!
Why would Sonos not acknowledge and admit a bug?

I’ve been developing commercial software for over 30 years now and I know every company I’ve worked for has done this. There are bugs that we’ve not wanted people to know about before we’ve fixed them. OK it will be in the release notes when the fix has been done but it’s quite often best to not publicise certain issues. I’m not saying that Sonos does this, I’m just saying that every company I’ve worked for does this and so we can’t with 100% confidence assume about known bugs in a system 🙂

[...] However, I'm really not convinced that every problem encountered with the software is network related.
There isn't a known bug related to the Controller app either.
Surely most bugs are unknown until they're discovered...

I’ve been developing commercial software for over 30 years now and I know every company I’ve worked for has done this. There are bugs that we’ve not wanted people to know about before we’ve fixed them. OK it will be in the release notes when the fix has been done but it’s quite often best to not publicise certain issues. I’m not saying that Sonos does this, I’m just saying that every company I’ve worked for does this and so we can’t with 100% confidence assume about known bugs in a system :)
I imagine this applies mostly to bugs unknown to the public. What does not affect me will not hurt me.

I’ve been developing commercial software for over 30 years now and I know every company I’ve worked for has done this. There are bugs that we’ve not wanted people to know about before we’ve fixed them. OK it will be in the release notes when the fix has been done but it’s quite often best to not publicise certain issues. I’m not saying that Sonos does this, I’m just saying that every company I’ve worked for does this and so we can’t with 100% confidence assume about known bugs in a system :)
I imagine this applies mostly to bugs unknown to the public. What does not affect me will not hurt me.

Yes that’s exactly what I was saying. Unless a person works for the company and knows everything about the software, they should not be telling people that there are no known bugs in a piece of software.