Working furnace but smell like electrical fire
The filter placement looks incorrect to me. Every furnace I've seen has the filter on the other side of the venting into the fan box, causing the filter to be pulled tight against the opening. With the amount of air my furnace pulls, it would pull the filter away at the top and bottom allowing unfiltered air into the system.

My theory would be that the unfiltered air is allowing dust and lint into the heat exchanger and when it builds up enough it is burning off.

A quick image search should give a better visual of what I'm describing.