I did a fall cleaning of the stove and chimney a few weeks ago. I swept the chimney, pulled and dusted the cat, Shop-Vaced the upper part of the stove out, ect, everything looked good. It has been a very mild fall for us. I had only built a few small fires using two splits per fire, while OAT was in the upper 50F. Not ideal draft conditions but the 3 year CSS oak was very sluggish to get going (no kindling as usual, about one cubic inch of Wally World brand fire starter). The draft actually seemed OK, it wasn't that the stove was rolling smoke out the door, just took forever to get going, so I had to leave the door cracked open, never had do do that before and I've lit fires with OAT in the mid 60'sF (only source of heat ). Anyway, we finally had an overnight low in the mid 20'sF and I got to build a decent fire with 3 splits- same lack of get up and go- had to crack the door to get it going, still sluggish once established... The next time the stove was cool, I sucked out the primary air inlet with the Shop-Vac. Problem solved. Quick start ups with mild temps, everything back to normal. I don't have any idea what may have been blocking the primary. I looked in it before vacuuming and couldn't see anything but I'm glad it's back to normal now.
I should do the same to mine, it seems a little more sluggish than usual but it sure drafts better without that rag stuffed up the liner like I had for my first fire this year.
Didn't take long, I remembered that I changed out my 45 going into my liner last summer and while I waited for it to arrive in the mail I took off the old one and shoved a rag in there but forgot to pull it out before installing the new 45. Chit happens.
Spider webs? They can be very thick. And when you run the stove, the dust bunnies can build on them.. My 2 pennies. .
I vote for spiders to blame too. Couple years ago, one burner in the gas grille burned katty-wampus. Inside the burn tube was a thick white mass like cotton blocking the whole tube about midpoint.