I've had to have moulds remade (for free).
Another possible cause could be that the tubing is ever so slightly too short and is pulling on the mould. I think I've had this problem in the past which caused discomfort where the top of the mould touches the ear.
Severe-to-profound hearing loss in both ears.
SD @ 100db L-88% / R-96% - unaided
Phonak Naida IX UPs