It seems unusual that 4 sets of AirPods have all developed a similar fault. There are 2 different types so it is unlikely to be common hardware defect, more likely to be the way you are using or the environment where you are using the AirPods (noisy?)
I suggest you start by checking your AirPods are cleaned with nothing blocking the microphones.
How to clean your AirPods, AirPods Pro, AirPods Max, and EarPods - Apple Support
Then check how you are wearing the pods, nothing obstructing the microphones.
I would also check the pairs of pods (of each type) are really pairs and you don't have the left pod from Set1 and the right pod from Set2.