I know that there have been many problems with saving achievements/XP/etc lately. While sometimes lost items will be returned, the achievement Stingy Jack has not for me, and I am permanently locked out of it as I have already found all 131 Jack o’ Lanterns. I recall seeing the “Quest Complete” banner show up, hearing the achievement jingle, and seeing it appear in chat however my game crashed shortly afterwards and I have no screenshot of me unlocking it.
As such, I have compiled an album of screenshots as proof that I have indeed, found all 131 Jack 'o Lanterns an am requesting assistance with having the achievement unlocked (provided Steam is willing to register it as unlocked properly.)
https://drive.google.com/drive/folders/1y9cKr48wKJSQbU7S1FkR4ay6IUy5knbB?usp=sharing
(if I missed any in this album, I may have accidentally skipped over some after consulting with a guide three times and performing many cursory searches)