Hey man! I had never visited this website in the past, so I hand't seen your post until now. If you're still struggling with this, know that what Facebook did was offload the contact sync features to messenger to force everybody to get messenger. So if your facebook messenger app is hosed or if you didn't reset it or give it the right permissions when you refreshed your phone, that's what the interrupt is. If you install both from the get go with all of the
"phone home" level permissions it will allow this functionality without problems like you expect. I for example, have a rooted custom Android 6.0 rom which has Super SU policing what and who wants what level of access, that affected Messenger's ability to access my contacts and therefore broke my sync as well.
Hope this helps!