I've had good luck using awesome spray cleaner from the dollar store or reliable 1 from Rv shops. They have both removed the yellow haze off of plastic for me. The trim around the door window is bad for yellowing. Give either a try, you will love either product.
Used this on the last two TT's, so far haven't had to on the 5er but we keep a gallon sized jug at the house and I keep a 16oz spray bottle in the camper.
Go Mark Martin? 2003 F-350 SRW CC/LWB 4X4 7.3PSD
2011 Keystone Cougar 327RES
Piedmont area of NC