Success! GPS, bluetooth and Wi-Fi all back at full speed
GPS was the first problem, blinking (off and on) regularly and returning crazy positioning (jumping 50 feet suddenly). Leter, Wifi also blinked.
Since we had replaced the batter last year, this install was very similar, same typical issues (takes 2 tries to get the screen reconnected at the end), only took 30 minutes. Turns out the original cable had a partially broken pin, which came off completely when ribbon cable was removed.
Success! Highly recommend this iFixit! these cables are a weak point in the iPhone design, and can break with rough treatment of the phone (what, you never dropped yours?)
We are back to 100%, and the GPS is accurate again. Finally I can use the map app.
watch the many youtube videos, and take your time. if it's your first time in the phone, it helps to have a helper who can hold the screen part while you focus on the connectors. Also, expect the screen not to work upon re-assembly, but don't worry, it just takes a try or two to reconnect it, and it's fine.