I got an Imp001 a the PCB I made, it works fine for days, weeks, months, but suddenly it just drops offline and never comes back online again.
Only way I have found to get it back online again is to cycle power to it, and when I do that, it starts blinking like this
https://www.youtube.com/watch?v=tr19uB3lCO0
Doing a blink-up on it brings it back again. Any idea why this could happen?
maybe you have a while loop in your code that it hits at some point and is then lost?
No loops in the code that would make it lock up, and it would not explain why it need to have a blink-up before it connects again.
Only thing I can think of is the code that makes it jump to another SSID when one goes down, but it has done that multiple times before without problems.
It looks like it’s trying to connect to a network and failing - I’m guessing it is in your reconnect code/SSID switching code.
The most recent blog post on the community blog is about debugging disconnected code - may help you better understand what’s going on 
I tried to entirely remove the stuff where it tries to connect to another ssid when one fails.
This was the code I used for it, just with the led switching removed from it
Does the Router you’re using have a syslog? I sometimes get valuable info from the router itself.