I would just comment that if there is an adhesion problem between the paint and the properties of the plastic from that batch run. Two things you should think of

If you dont sand through the existing paint. the new paint will fall off when the rest of the old paint does.

If E had problems getting the "right" paint to adhere to the that batch run. It may be a challenge to find a better paint to replace it.

There are good paints and surface preps for plastic. Sounds like a better idea to let them replace them for the long term.

just some thoughts,

Bill