As noted, there is a specialty tool for cleaning out the 'heel' in front of the firing table to prevent the observed kind of heat damage 'from below'. I'd suspect something like that could have been used to keep coal from reaching ignition on the firing table, since I'd expect it would need considerable 'dwell' to ignite and transfer damaging heat by conduction after piling up on the table. Particularly if no one noted the jet problem and left the elevator running to spill fresh coal on the table for distribution.

Perhaps when there was a jet problem there was some 'target fixation' in the cab about how to get the jet(s) cleared and working, while the combustion on the table was building up to troublesome level? This might be addressed in future with a 'checklist' to follow if there is some kind of stoker-system outage. I don't say this as armchair-quarterbacking but sustems improvement.

And if they don't have one of those tools in the cab, make one and ensure it's used appropriately when needed.