Going back tomorrow to clean belts and drum but they do look ok, got the belts from Sodica France European Otis parts distributer, checked with them and they have said there is no coating on the belts.
Managed to get hold of an official Otis belt cleaning kit so we will see how that goes tomorrow, if not next would be a half load balance test i suppose check it was balanced on installation although there was never an issue before with the old belts.

Worse thing is belts were fine until an insurance man buffered the CWT, not sure how he managed to do it as we couldn't replicate it but it appears the lift car top shoe impacted one of the belt monitor clamps and damaged the monitor and put a small rip in one of the belts....