I agree with lakeside. This is usually down to your drying practices, but it could also be due to harvesting too soon, which a ton of people do.
I never really considered harvesting too soon as a factor - good tip
I only speak from recent experience with proper drying and curing - I saw my grow space now to get the job done, being able to perfectly dial in temp and humidity have been key for me. I would also recommend picking up some of those tiny hygrometers on amazon that you can toss in ur jars during the cure; it helped me build confidence in getting it right.
I was just trimming up some white widow today - just straight burnt plastic, gas and the unmistakable smell of fuzzy peach candy, when I realized it I tripped out lol