Problems with synchronizing speed dial buttons between Yealink MP56 E2 and Yealink EXP50

Hello everyone,

I have the following problem. We have several Yealink MP56 E2 Teams phones with connected Yealink EXP50 key extensions. Unfortunately, for about half a year now, the synchronization of speed dial keys between the phone and the key extension has only been possible to a limited extent.

Specifically, you can create contacts on the phone and add them to speed dial via the phone. However, in 99 out of 100 cases, this is not synchronized. The same applies to deleting contacts. What's strange is that the deleted contact is not actually deleted from the phone itself and reappears after 2 seconds.

I had already read that this error has occurred from time to time in recent years. Unfortunately, there has been no noticeable improvement in the last six months.

I have already tried the following:
Resetting the phone, rebooting after changes, disconnecting the connection between MP56 E2 and EXP50, logging back into the phone, updating the phone's firmware and the phone's Teams app.

Unfortunately, none of this has been successful. Does anyone else have any ideas or has Microsoft made an official statement that there are problems here?