[Nexus 5 Android Development] pringled:
I was hoping it was because you've had a similar problem and wished to impart on me the easy and quick solution to fixing it that you had discovered, but I do appreciate the well-wishing ;)

I don't know why it suddenly clicked last night, but while I most certainly did not find a solution, I did however find two more commonalities re; what (in my case, anyway) buggers stuff up:

1)CM12-based ROMs are affected the most severely by it (ROMs with this base are in most cases completely unable to establish a network connection for me, and the one exception disconnects with extreme regularity)

2) While it's obviously always ideal to flash the recommended gapps for your ROM to avoid hypothetical issues I've seldom followed that rule and instead gone the "just flash any random gapps package that's current" route and have only been hampered by it in the slightest maybe 5 or ten times max out of the thousands of occasions over the years in which I've flashed a gapps package, spanning 9 or 10 or so phones. In this case flashing the recommended package seems to make such a difference that they're less recommended and more essential. Last night I fell in love with the Twisted Android Project ROM, only for the connection issues to render it unusable when I was no longer using WiFi. I loved it enough that I decided to try it again with the suggested package even though it was almost the same size as the ROM itself as opposed to the preferable 100mb-ish size of the one I initially used... and it completely fixed my the connection issue! This inspired me go back and retry a bunch of ROMs I liked but had stopped using as the network connection problem got to the point of usability on them, and in a lot of (but not all) cases the problem was either fixed or way less severe.

The fact that at some point post-late June when this clusterduck first started occurring and the last of my fav ROMs ceaed to function entirely properly for me, the only ROM I've used that NEVER had the connectivity issue was Cataclysm... which has it's gapps package included in Aroma, makes me think that either:

a) that this is and has ALWAYS been a problem that arises for ALL ROMs on ALL phones when you flash a style of gapps that isn't the one the devs suggest, but somehow I lucked out hundreds or thosuands of times and just happened to flash the correct one by happenstance every single time I swapped ROMs on every phone I've had for the last 4 or 5 years, but that luck ran out ENTIRELY almsot two months ago,

b) whatever the root of the network connectivity bug is also either is (at least partially) remedied by something abut using the recommended gapps, OR makes using the suggested package as oppsoed to any package that is up-to-date an absolute must.

or

c) Same as B, but this has always been the case since the issue first started arising for certain groups of people with the arrival of 5 to begin with and I'm just an idiot and never thought that maybe it's some sort of new incompatible gapps problem that wasn't an issue on 4.4.4 and prior

Unfortunately I started forming and testing these theories right as I was going to sleep last night, and then this morning I managed to start my day not with my usual coffee-and-a-poop bur rather with breaking the screen and possibly digitizer on my phone, so unfortunately I didn't get to pointedly reflash anymore previously affected ROMs alongside their dev-endorsed gapps and get a large enough sample size to make a declarative/definitive statement. Granted, as I said earlier the most vast majority of active and current threads *****ing about this problem were on sites that didn't cater to the kind of phone owner that even roots their phones, let alone flash ROMs as a rule, so that might negate the gapp-fix being anything more than a one-off for me. Also, the breaking-my-phone-when-I'm-broke part was kind of unfortunate as well, I guess.

Anyway, sorry for the long-winded post, maybe someone else who's been having this major issue as well wants to give it a shot on a number of ROMs that had ceased working for them as well and see if my suspicion holds any weight. I'm really hoping that it does, but even more so I'm hoping tha I have;t inadvertently made myself look like an idiot. The irony of all of this is that even if I am right, by the tim I can afford to get my 5 fixed M will be out and this problem, whatever it may be, will be gone and a whole host of new ones will be in its place, lol. Hope this helps someone!