Green substance inside airpods case

This is my 2nd airpods which started showing a green color substance inside the aiprods case. The material actually stays near the charging point and cause a charging issue.

First it happend with my airpods 1 and they just stopped working and Apple support was as useless as they are. Instead they charged me to get the airpods replaced.

Now, i bought the Airpods Pro and now it shows again a green substance inside. Is any one facing the same issue?

I think the airpods battery is leaking that is why green colored substance.