coal falling off sides of the grate

Hi all,
This my second season with a stoker. I'm running an Alaska Cast Console Hearth model. I've just started getting rice coal mounding up on the grate and a small amount falling of the sides. I'm using lightly oiled rice. I used untreated rice last year. The oiled rice is dry to the touch. Combustion fan shaft is properly lubed. I keep the low fire and high fire settings within 1 to 1.5 points of each other. Stove is running fine otherwise. Any experience with this?????????
Thanks and happy New Year. Tom

From delivering I can tell you wet coal will stick to the chute, you need slightly more pitch than if it were completey dry particularly with rice. Same may true with the oiled coal, simply not enough pitch, even if its just a little film on it.

You might have something stuck to the grate, clinker or fused coal to the grate. it stops the ashes/coal from pushing smoothly/evenly off the end and it backs up and some falls over the sides of the grate. You may have to shut it down and scrap the grate good and sand it smooth. I had it happen with a big clinker, it stopped the movement and everything decided to go over the sides of the grate....

Ahhh, WNY is correct, any obstruction no matter how small will stop/slow it too. One frozen piece of rice on the chute could stop whole operation if it's barely going to begin with.

Thanks Richard and WNY. There was a 1/2" X 1/2" obstruction on the grate. Needed a hammer to get it off. Working fine.
Tom