With those test results it is clear this is not a coal-trol malfunction causing the problem. The stoker on times match up with the FR's and MAX setting.
Need to be looking at the combustion blower, air holes in the grate, the change in coal (smaller coal will result in incomplete burns since the air has a harder time getting through the bed), might want to take a sample of the coal to a different supplier and compare against their rice coal to see if there is a significant difference. If there is, you may need to buy some buck sized coal to mix in with your smaller sized, which will open up more air passages and allow for complete burns.
I understand you said this started before the new coal load, but it is possible the bottom of your previous load was comprised of the smaller size or that the smaller sized stuff had settled to the bottom over time.
1) Does your combustion blower have a restriction plate on it? Has the position of it changed? Try opening it up.
2) If no restriction plate, is the motor turning at full blast, unobstructed, and the blower/cage blades aren't plugged up? Clean it thoroughly if needed.
3) You cleaned out the grate and air chamber beneath it, are you sure you poked out all the fines from all the holes?
4) Coal size. Compare against the sizing of a different load of rice coal from another supplier. If it seems to be sized significantly smaller, buy 40-80lbs of buck to test some mixes. Start off with 1:3 buck to rice, move to 1:2, and then 1:1 after trying to burn each mix.