OK, the camera is now back from Fuji. It has been fully repaired as stated in the brief report. No explanation of what caused the issue though. So far so good.
There are small fibre glass pens you can get specifically to gently rub contacts in the camera and clean contacts without touching them. Finger grease etc... is going to make it worse. They are readily available and cost a couple of dollars. Something like the link below. Most times this will cure the issue if its oxidation.