Rheem furnance blows cold air

I have a Rheem criterion gas furnace that blows cold air for 40 minutes after the heat cycle is off. I opened the panel and there is a yellow/amber light that is blinking. HVAC tech came replaced limit switch but issue still persists.

The furnace will start up, go through entire heat cycle without any problems. It reaches the correct thermostat setting temperature but blower fan does not stop 40+ minutes, blowing cold air, and the amber/light LED starts blinking fast again.

Thermostat setting is set to "auto". Please help with any advice!