Soundstation IP 6000 works only for a short time after reboot

[Anonymous]

We are using the Soundstation IP 6000 internally with our PBX (Auerswald COMmander Basic.2). When the device is booted, everything works perfectly fine at first. It registers with the telephone system (connected "black telephone-symbol" is visible) and it's possible to make and receive calls.

However, after a few mintutes, this stops working. The telephone still seems to be connected. However, when calls are not received and when trying to make a call there is just a beeping sound. To make it work again, I have to reboot.

Any ideas to what (mis-)setting this could be related? (Maybe it has sth to do with our PBX, but I hardly believe so. After all, it's not our first IP phone.)

Configuration (non-defaults):

IP: 192.168.130.128

SIP

+ Local Settings:

+-- Local SIP Port: 5060

+ Servers

+-- Server 1:

+---- Address: 192.168.130.178

+---- Port: 5060

+---- Transport: TCPonly

Lines:

+ Line 1

+-- Identification:

+---- Address: 73@192.168.130.178

+---- User ID: 73

+---- Password: (none)

+---- Label: 73

+-- Server 1:

+---- Address: 192.168.130.178

+---- Port: 5060

+---- Transport: TCPonly

[Anonymous]

Changed TCP to UDP. Seems like this solved it.