Native Bridge Problem on tdm400

i have a tdm400 with 1 fxo and 1 fxs

the fxo works fine, can make and receive calls from my SIP phones
i can also receive calls on the FXS port.

however the problem starts when i make a call from the FXS port to the FXO.

it dials and connects then i get really loud noise on the handset and it fails

see output below

– Starting simple switch on ‘DAHDI/2-1’
– Executing [123456789@FXS:1] NoOp(“DAHDI/2-1”, “—123456789 calling on FXS port to —”) in new stack
– Executing [123456789@FXS:2] Dial(“DAHDI/2-1”, “DAHDI/1/123456789,30”) in new stack
– Called 1/123456789
– DAHDI/1-1 answered DAHDI/2-1
– Native bridging DAHDI/2-1 and DAHDI/1-1
– Executing [h@FXS:1] NoOp(“DAHDI/2-1”, “—h calling on FXS port to —”) in new stack
– Executing [h@FXS:2] Dial(“DAHDI/2-1”, “DAHDI/1/h,30”) in new stack
[Aug 29 08:10:53] WARNING[3667]: app_dial.c:1468 dial_exec_full: Unable to create channel of type ‘DAHDI’ (cause 0 - Unknown)
== Everyone is busy/congested at this time (1:0/0/1)
– Executing [h@FXS:3] Hangup(“DAHDI/2-1”, “”) in new stack
== Spawn extension (FXS, h, 3) exited non-zero on ‘DAHDI/2-1’
– Hungup ‘DAHDI/1-1’
== Spawn extension (FXS, 123456789, 2) exited non-zero on ‘DAHDI/2-1’
– Hungup ‘DAHDI/2-1’

no idea where the h@FXS has come from !