T28P Handset Noise Problems

[anonymous1712222627012]

Dear Support,
we have same problem with T26.
At the moment we have installed more or less 900 pcs.
We observed a 10% of faulty handset.
The problem is a noise listened (as 50Hz buzzing),
but the issue come out after a short period of using (like 1 or 2 month) not immediately soon installed.
My opinion is the cause is the welding on the electret microphone.
I had same experience issue with telephone of other vendor .
Immediately Solution (workarround); give it a "shot" at the handset.
Definitely Solution : change the handset.
Repair the Handset: replace the welding or remove the "silicone" on the welding.

Sorry but I have not the serial number of the telephones affected.

Regards
Walter