Running raspbian (still on armv7) headlessly to serve up a few container services. It’s worked for a few months now no issue. In the last couple days, I updated all the docker images and raspbian. Now I’m having an issue were it drops connection (wifi and ethernet) all together.
My first quick attempt at a fix was to swap out the 4 with an old 3b, this did not work. The 3b was up ~16hrs before dropping connection. So prob not a hardware issue?
Any ideas?
At first blush, I would recommend trying to roll back raspbian to the previous version until they get their network stack sorted. If that does not work, let me know and we can walk through it 
This sounds really silly,I know, but do not cheap out on your power supply. I’ve got a Raspberry Pi 4, which developed weird software problems after working just fine for a while. And the solution was to use a different, better power supply, plus image a virginal MicroSD card and start all over again. It ended up not being a software problem, but rather a hardware problem, which developed over time, like a few days.
Please use a pristinely-suitable power supply, ideally their official one.
@esbeeb I should pick up the official one, at least to rule this out. I am using one that came in a kit my wife bought me, it specs just fine though.
Update, I booted it up and left the 3b running with hdmi connected. After a few hours, I got a kernel panic screen. Something about the BCM83… (my wife needed the tv so I didn’t have time to record the info). Initial thoughts though are an issue with the latest update or it may be the power supply. I run 2 powered 3.5 hd’s and 1 non-powered 2.5 hd. I’m just guessing rn though.
I will be trying to pull whatever data I can, using a new sd card and just re-start. That’s why I’m using docker right and, this time I can use the v8 kernel.
I used a 4A great quality OnePlus phone charger, thinking, surely that’s enough power. But the RPi4 hated it. Wouldn’t boot a perfectly good, quite new Sandisk MicroSD card. I switched to a 3A phone charger, for a Xaomi phone, then the RPi4 was happy, all other hardware staying the same, even that MicroSD card.
Raspberry Pis can be fussy about their power supply being just perfect!
Some of the first revision of the Pi 4 were missing a resistor. This caused a bunch of third party chargers to not work. If you have an unrevised board, you might be able to fix it yourself with a soldering iron and connect a 5.1K resistor between CC1 and ground.