LG TD-C70045E Clean Filter error but filters are clean

Hi. My LG tumble dryer stopped mid cycle recently with ‘Clean filter’ error. There was also a faint smell of burning. Our filters are clean.

Here’s what I did to attempt to solve it – BUT it did not fix the problem. The dryer runs and heats for 2 to 3 minutes then stops with the beeper and ‘clean filter error:

I removed rear fan and heater cover to reset the trip button but that did not resolve it.
I then removed the top, both sides and front panels (including door and the switch panel. The inside was surprisingly clean.

I also removed the housing of the first fan before the electric motor (again quite clean inside).

I cleaned all airways, the blades on both fans, the filters and the sensor under the bottom door filter (which was a little gunky but now shines!). I removed the little fluff around the inside of the unit on ledges. Then reassembled BUT it still cuts out after 2 to 3 minutes with ‘clean filter’ error.

What have I missed or what parts do I need to replace please?
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