Another stand out in problem reported is 2nd ton having more 'powder' and/or fines.
Damp coal dust will fill gaps around the aluminum pusher block and make a paste that will become near cement as it dries.
You may of noticed signs of this at your past clean out.
It is this drag on pusher block which will allow the motor arm w/ bearings to strech or force open the forks spacing.
With widened foks coal feed rate is reduced and that can equally reduce heat output.
The manual makes reference often to not using wet coal, and boy has it been wet these past couple months.