Patio legend 410

Bought this in August, have around90 cooks on it, has been great. All of a sudden I noticed it was taking a really long time to light. I started it and it took 15 to 20 minutes to light, I closed the lid and went to my chicken wings, came back and grill was engulfed in fire. Too 5 gallon bucket of water to put out. Grill was not dirty or grease build up. Fire pot was empty , so started it apart and watched the pellets dump in for a good 15 minutes, it started to light and fire ended up being huge from the pellets, what could be causing the slow ignition,