DECT Phone on LDK24

[jezt]

I have a LDK23 system with 4 analogue lines in.

I have 3 LG hand sets, 4 LG 450 DECT phones and 2 GDC 400 base stations.

Recently the DECT phones have stopped receiving calls.

If I dial 10 from one of the DECT phone is says call from handset 33.

Dial 33 back and it come up with "NO RESP".

I've tried de-registering the handsets, but if I then try and register it says in use.

Is there a way of resetting the WTU.

Cheers, Jez,