M700 and M25 freeze

Hello, this is my configuration: 1 Base DECT M700 + 4 cordless M25 

PBX: Yeastar

Firmware base: 530.10

Firmware cordless: 530.10

Problem: During a call an incoming, in the transfer call or in hold to another M25, the cordless freezes, the interlocutor hears the music on hold, we hear what he says. Only option is to hang up and this finishes the call obviously. Tried almost everything including a hard reset and fresh start of the configuration. Any help please would be greatly appreciated.

Thank you