Sony WF-C500 TW left earbud failure

Hello!
I recently got great (for the price) True Wireless headphones from Sony. This is the WF-C500 (Black). At first, he calmly did his job admirably. The case charged quickly, the headphones had great connectivity with the mobile device. But for some time. After about a month the problems started. The left handset has the function of answering calls when the button is clicked on it, unfortunately at that time it was broken as an emergency, because it turned off the device completely (you had to put it in the case to start it). The left earphone also turned off by itself.
Now on to the actual case:
As I said, the left earphone was failing until it died completely. Sometimes it was "kindly" possible to start it (start up in the case) but after taking it out of the case, nothing can be heard, and the handset dies again and it needs to be started up. But the problem is that to be able to use the left earphone you have to wait until it boots up and goes into charging state; it only takes a few seconds to start it but it does what I was talking about earlier. I've read a lot of information on how to fix it, on the websites of online stores, forums, on the official website of the manufacturer and in the official manual, but nothing helps.
I got these headphones as a gift because I love music. These headphones were great, had great sound, nice style, long battery life and they are still like that, not counting the left one with which I am helpless ...
I'm still under warranty, but I wanted to ask here if anyone has encountered similar problems and if anyone could advise something.
If you are such a nice and sympathetic person, could you help me in this situation?