I can't imagine what is going on especially since you get warm air and hear them crackle,
I clean mine with hot water...pump water thru them using a baby syringe....then pump air through them until no water comes out,,,dry them at 225F in the oven for an hour and they work fine, Usually only take about 3 puffs to get them going again,
I would suggest destroying one of the 808's to see what is really going on inside (you would be turning it into a drip tip so it wouldn't really be destroying it,).
Take out all of the foam inside of one, leaving the center tube and being careful not to pull on it....then hook it up on your manual battery. Hit and hold the button for about 5 seconds and see if it begins to glow red inside on the wire/coil. Repeat if necessary. Then drop a couple of drops of juice outside of the tube and hit the button again, You should soon be seeing some vapor. Don't be afraid of repeating the 5 second hold a few times, At this point you aren't worried about burning out the atomizer inside since you've already mentally assigned this one to R.I.P status. You should be able to put a drip tip on it now (or just your cap for the time being,,,or nothing, just don't burn your lips) and use it as an atomizer.
Still not working? Take the now naked cartomizer and rinse it really well (soak for 5 minutes, then rinse) in alcohol...the higher the percentage of alcohol (I use 90% rubbing alcohol) the better and the quicker it dries/evaporates. Pick up the carto/atomizer like a little cup full of the alcohol and it should be dripping or running freely thru the hole in the bottom,
Wipe off the outside of the unit, blow out the remaining alcohol first from one side then the other, then put it back on the battery and push the button to burn off any remaining alcohol. It should glow nicely now.
Now you can drip directly into it 2 or 3 drops at a time and use as a drip atomizer.
'IF' this works then you know the cartos are still good, they just aren't getting cleaned and dried as they should, Maybe they have mega build up,,,I don't know,
'IF' it worked with the one you just did those steps to, take the others and re-clean using a baby syringe (Walmart- $2) and hot water then dry again in the oven as before,
Hopefully, this does the trick for you.
I can imagine how frustrating this has been for you,
PS. If your cartos are the ones ceramic type that you fill with a syringe the problem just got harder, You would have to destroy the first by removing the rings inside then doing the alcohol thingie with, I haven't tried to simply convert that type to atomizers for dripping before so I don't know how it would work,
Good luck
Keep Vaping!