Drafts pulled into house when furnace blower turns on
Your furnace pulls air from your house (that return vent in the ceiling), heats it, and then blows it back into the house (the floor registers). It should pull out the same amount of air that it blows back in, but your experience shows otherwise; it's pulling more air out than it's blowing back in.

It looks like some of the (heated) air isn't making it back into the house. If, say, 1/4 of the air that's pulled from the house passes through the furnace is discharged to the great outdoors, then you'd have to have the same amount of air being pulled back in through "cracks and crevices" in the building envelope. If not, after a while the house would start deflating like a leaky balloon (and, since you didn't mention it, I'm guessing that isn't happening).

So, somehow hot air coming from the furnace is leaking outdoors. Check the furnace housing, check those ducts in the crawl space, check whether there's (warm) air blowing outdoors from the crawl space. Also try and compare the amount of air coming out of the registers to the amount going back in the return.

Good luck.