FR 245: fast battery drain after sync

Hello, the Forerunner 245 Music watch, while there was no synchronization with the phone, the battery consumption is normal. But as soon as I connect the watch to the phone, the fast battery drain starts. It does not stop even after disconnecting the watch from the phone, the watch probably continue to search for the phone, although I disconnect it (maybe incorrectly). Only a full reset to the factory settings helps.

Where could the problem be? I can’t do a reset after each synchronization with the phone.