Hi
This seems very strange but there is a verity of things it could be
1)it could be a bad connection due to it not being seated properly
2) it could be damage to the connector however if you look at both connectors (cable and board ) it should be fairly obvious if something is bent out or deformed
3) it could be some invisible dirt that our human eyes can see that needs cleaned off with a cotton bud and some isopropyl alcohol
If you try what I have mentioned and still have no luck please let me know and we can look into it further
Hopefully this helps
Any questions please ask
Thanks:-)