Porter cable 7424xp not working correctly

I have a pc 7424xp. I now mainly use it with a 3 1/2 inch backing plate for hard to each places. I pulled it out to work on a stubborn oxidized headlight. The porter cable made a clicking sound, like an electric drill with a clutch adjustment on it. It was spinning but didn’t seem to have any random orbit to it I used it for 15 seconds or so trying to get one oxidized area and it seemed to burn the plastic headlight and left a cloudy spot on the plastic. . The pad was cool but the headlight was hot, not warm, to the touch.

Two questions: 1. Any idea what is going on with the polisher. 2. What is the best way to clean off a “burnt” area on a plastic headlight.

It is on a friend's jeep Cherokee. The headlights initially looked awful, looked like someone had smeared mayonnaise on them. For the most part, they cleaned up really well. Just a few really tough areas that were still hazy. Those were the areas that I was trying to fix.
My friend is a young guyin the navy. He is about to graduate from some really intense, year-long training out here in Coronado. I was trying to do him a favor. He had dropped by to chat and was getting ready to leave. I noticed his super bad looking headlights. I told him to hang on a second so I could try to clean them up for him. Gotta keep our warriors cruising in style!

I was using optimum spray compound and spray polish with lake country orange and white pads. I was using my flex 3401 for most of the time and I pulled out the porter cable to polish the recessed fog lights. There was a small line of oxidation that wouldn’t come clean on a headlight so I thought that I would try the Pc to concentrate on that spot I have never run into anything like this before.

The burnt/ cloudy area is about two inches long and snout 1/2 to 3/4 of an inch wide. Somewhat of a slight crescent shape. It is an hazy, whiteish color. The rest of the headlight is now really clear. He was really happy with results. I am mortified. Thanks. Sorry no photos. Phil