Cleaned HVAC ducting may have or should have been internally sealed (think of a thin spray coating to seal everything in place = clean, fresh surface). A sudden increase in odor may be suggestive of something heating up and cooking the smell out again. You might call in an HVAC tech to check out the closet unit for something that could be getting hot on the way to failure.

Is it a free standing house or a condo or an otherwise attached unit? Do any neighbors smoke?

Free standing

It could be that the condenser coil or the filter had absorbed them in the past and now they're releasing that smell through your house. Try changing all the filters if you haven't and take a look at getting the coil cleaned if it hasn't been in a while.

Twintech Heating & Cooling

https://twintechheating.ca/