Can’t get rid of the burnt hair smell with my heater on

My heating equipment smells like burnt hair anytime I turn it on.

I am driving myself crazy trying to eliminate the burnt hair smell.

First, I tackled the furnace filter. I cleaned the filter and tried it again. That did not work so I bought a whole new one. I then took my furnace totally apart and cleaned the inner workings. I dusted, vacuumed and wiped anything I could find. I removed huge chunks of hair and dust from the heater. You would think that would do the trick. Nope, the heating technology still reeks when it turns on. I thought I had a brain blast the other day. I called my HVAC company for ductwork cleaning. They say every 5-7 years the air ducts need professional cleaning. I could not remember the last time so I figured that is where the hair must be. I had the HVAC contractor really clean every little bit of ductwork. I even paid him extra to take his time with it. That is how bad I hate the burnt hair smell. He showed me all the gross debris he got out of my HVAC ducts. I was excited thinking my problems are all solved. Well I just ran my heater equipment and it still reeks. The smell is a little better, but I can still smell burnt hair. Is the hair deeper in my heater than I thought? I am thinking that maybe I need a professional to take apart the heater. I might even buy an air purifier I hate the smell so bad.
Can’t get rid of the burnt hair smell with my heater on