The last couple days I have noticed that the spray width on my PG gets narrow after long runs. I did find that the screen was partially plugged once, but I cleaned it and the spray width was back to normal. But since then I have noticed that the spray width will vary a couple feet during long runs and that the droplets coming out do not look evenly dispersed. I have 64 hrs on the unit. Could it be the pressure valve in the tank or is the belt getting worn and starts to slip when it gets hot?