Overnight, the AirPods case is completely discharged to 5-9%

I have AirPods. I charge the AirPods to 100%, then I use them for a short time. Then I put them into the case fully charged to 100%. The headphones lie in the case all night. And in the morning there is a charge, it shows 5 - 9%, the headphones are 100%. The shop replaced the case. But this did not help, the problem persisted. I also restored the factory settings on the AirPods. I changed the cables and sockets for the chargers. I handed them over to an authorized service in our city, they cannot find this problem.