Try Scalecoat (Weaver) "Wash Away", a paint remover safe for plastics.
Of course, if your matte finish is over another paint...which you want to keep...you're in for a real problem. As 'slow-acting' as the remover is, to stop the action short of the base paint removal will be nigh unto impossible.
Best solution then?.....Remove it all and start over.
KD