do you by any chance have apple WiFi router?
i have a Time Capsule and after i updated to 11.5 my Time Capsule also started to blink orange.
it turns out that apple also released a firmware update to its routers about the same time.after i installed the update it was ok.
I'm replacing the router next week, but I suspect that probably won't help.
Asus did a firmware update not to long ago for my router (RT-AC68P) and it didn't help.