Followed previous thread and recommendation.
Reset Limit Switch and the unit will restart. Burner will fire and run until thermostat temperature is reached then the limit switch with trip at flame out, and the blower continues to run indefinitely until shut off manual at the emergency cutoff, thermostat control will not shut off blower.

Ducts and filters are clear. Any clues as to the issue?

You might try increasing the blower speed or, if possible, increase the delay between the burners shutting off & the fan shutting down.