2002 Santa fe with dash vent cover slowly melting
 

I bought my Santa fe new in 2002 and had the full treatment - tinting,
paint treatment, interior protection (by Ming Australia).
I noticed that the black dome in the centre of the dash that covers the
vents appeared a little soft and sticky but thought it was just the
treatment.
Now the dome is melting. If you touch it you leave finger prints in
the plastic.
Has anyone else had this problem?
I have only attempted to was it once with just water and this just
smeared the tacky plastic.
Help!