"Spiderwebing" probblem

Hey All
For the past few days ive been repairing a bumper on a family members lexus, and im now down to painting it, but there has been a few spots that have been reacting and causeing it to "spiderweb" and i have tryed and tryed and tryed to get it to stop, but it dosnt, im relitivety new to painting, but i have tryed everything i know to fix it, im using a flexabul primer(even that reacts) im sanding the surface, then using pre cleaner, then a tac cloth to make sure it it 100% clean, but still it keeps happening. Its to the point now im just getting pissed off. the areas that are reacting now are the areas that are down to the plastic, but i was always told the flexabul primer should solve my problem. If anyone can help me solve this it would be great.

ps im not spraying in too heavy of coats or not waiting long enough for it to dry before applying anothing coat.

Still nothing :( lol Well
I was working with it today, and i decovered that body repair shop thats name i wont disclose, did a terrible job on the bumper when it was repainted about a year ago due to faiding, but they didnt prep the bumber at all no sanding or anything because the paint they put on is just chiping right off, looks like they just washed it and sprayed. so what i beleave is happening is the areas where im down to the plastic the new paint is getting between the first and second layers of paint and lifiting it, causing the spiderwebing. but anyone what can confirm my theroy, or give me any other possible reason, it would be great.

Well you 2 problems from i read. 1st from i read that bunper was painted before. Now whoever painted it didnt prepare the surface good so that paint cant grab. The reason why your getting spider webbing is because the painter didnt put a flex agent while mixing the paint. A flex agent helps the paint flex without the paint cracking. To fix this priblem you need to sand 320 the whole bumper then re- shoot. Have the flex agent mixed in the paint.

If you sand or strip to bare plastic here is a good system to use called OneChoice (https://buyat.ppg.com/refinishProductCatalog/ViewProduct.aspx?ProductID=beaa9548-e3a5-4232-8422-2ccad827489a) by PPG. Click on the OneChoice link, than click the Tech Info (pdf)
(https://buyat.ppg.com/refinishProductCatalog/ViewProduct.aspx?ProductID=beaa9548-e3a5-4232-8422-2ccad827489a)
I'm sure other companies make good systems too. You can ask your paint supplier for suggestions.

Again, this is only if you decide to strip down to bare plastic. If you just sand through to the plastic in a few spots, just spray a thin coat of plastic adhesion promoter on it before applying primer.