In July, our ancient TRG60 finally expired when its water jacket rotted through. Our local heating engineer fitted a brand-new TRG, and Trianco promptly went through the hoop. Here's the rub - the anth grains left in the bunker, which the old boiler was happily using will not burn in the new boiler. I have also loaded it with beans, dry, pre-packed rather than from open bins, and it still goes out within 2-3 days.
What I have noted is :
1. No clinker, only ash - with either fuel
2. the fuel appears to remain mostly unburned (probably 60%)
3. what does burn is predominantly at the back of the grate - the fire does not spread forwards
4. Keeping the fan on by turning up the stat only makes a marginal difference to the time that it will burn
5. The fuel does not drop as readily through the regulating slot
There are two basic changes to the design that I can see - the fan is now central, and I think there is a secondary air path to the rear of the grate.
If the problem is being caused by a general degradation of the fuel, we are all sunk, because my experience of coal merchants is that they have all decided that they are in a dying business, and rather than seeking medical attention, they would rather stop breathing in the hope that their problems will go away.