Hi @valialexandru
Try a power refresh and check if that resolves the problem.
Open the headphones and disconnect the battery from the board then ''press and hold'' the on/off button for 20 seconds and release.
Reconnect the battery to the board and turn on the headphones and check if it all works OK or not.
Whilst the headphones are open, inspect the board for any signs of corrosion or other damage to the board's components.
Here's a [https://www.youtube.com/watch?v=8_thWyngtUs|video] that shows how to replace the battery that shows how to open the headphones