Comment 17 for bug 1613327

While this isn't a real fix, I have found a workaround for this bug so people can at least use their Pro5 without getting annoyed too much by this:

create a file /home/phablet/bin/swithto3g with this content (create the "bin" directory and make sure the file is executable):
----------------------------------------
#!/bin/sh

pref=`/usr/share/ofono/scripts/get-tech-preference | cut -d " " -f 3`
while [ "$pref" != "lte" ]; do
    /usr/share/ofono/scripts/set-tech-preference lte
    sleep 5
    pref=`/usr/share/ofono/scripts/get-tech-preference | cut -d " " -f 3`
done
echo $pref
-----------------------------------------

Then, create another file /home/phablet/.config/upstart/3gfix.conf with this content:
-----------------------------------------
$ cat .config/upstart/3gfix.conf
start on started unity8
exec /home/phablet/bin/switchto3g
-----------------------------------------

This will, on every reboot, run the script which will in turn will set the tech preference to 4G. Seems to work well for me so far.