I think it could be your batteries that are the problem here, AWT are a rewrap company and have a track record of supplying some notoriously shit batteries, sometimes some of them are OK but they can change the cell under the wrap without warning so you can't rely on any particular cell in their range being consistent.
I'm not familiar with the other batteries you mentioned but the fact it has 40 Amps written on the battery wrap rings alarm bells (and you mentioned they are old so they are probably well past their best anyway.
40 Amp 18650s DO NOT EXIST.
Just for reference - the higher the capacity, of an 18650 the lower the Amp rate (and for single 18650 mods you must use high Amp batteries for DL vaping - and the higher wattage you vape the higher the Amperage you need.
If an 18650 has 3,600 mah the highest AMP rating it can have is 10 Amps (these are good for MTL or low power RDL, but they aren't any good for over 25 Watts)
If it has 3,000 to 3,100mah the highest Amp rating it can possible have is 20 Amps (good for 60W MAX)
If it has 2,500 to 2,800mah the highest Amp rating will be 25 Amps (good for 75 Watts, even when the battery is low, but they will discharge really fast at that type of load)
There are a few 18650s up to 2,100mah that are rated for 30 Amps, but these are rare and I haven't seen any in years
If you see any 18650 claiming over 30 Amps, or claiming over 3,600mah capacity IT IS A LIE. Nor will you get any higher Amp rating for a set capacity than the ones I've listed above - i.e. a 3,000mah 30 Amp 18650 does not exist - a 3,000mah capacity will only be rated for 20 Amps. Unfortunately battery re-wrapping companies know that printing ridiculous claims on capacity and Amp capability helps them sell batteries so bullshit specs are routinely printed on rewraps.
Personally if I was vaping at 50 Watts or under I would go for 3,000mah Samsung 30Q or Sonly VTC6. At over 50 Watts then either Molicel P26a, Molicel P28a or Sony VTC5a.
Whatever you do, DON'T buy any more 40 Amp 18650s and avoid AWT batteries as they are mainly shit. Try Fogstar for your next ones as they don't stock batteries with inaccurate ratings.
And
@Richard Winter 's tip about keeping your battery terminals clean is a good one (try sticking a pencil with a rubber fitted to the end to clean the ones up inside where they are hard to get to with your fingers.