I would like to ask about a real cause of  disconnect  voice connection based on the result which is bellow.
Log from Cisco router.

ISDN Se3/0:15: RX <- SETUP pd = 8  callref = 0x1A52
        Sending Complete
    Bearer Capability i = 0x8090A3
    Channel ID i = 0xA18392
    Progress Ind i = 0x8183 - Origination address is non-ISDN
    Calling Party Number i = 0x01, 0x81, '11111, Plan:ISDN, Type:Unknown
    Called Party Number i = 0x81, '22222222', Plan:ISDN, Type:Unknown

ISDN Se3/0:15: TX -> CALL_PROC pd = 8  callref = 0x9A52
    Channel ID i = 0xA98392

ISDN Se3/0:15: TX -> PROGRESS pd = 8 callref = 0x9A52
       Progress Ind i = 0x8188 - In-band info or appropriate now available

ISDN Se3/0:15: TX -> PROGRESS pd = 8  callref = 0x9A52
    Progress Ind i = 0x81B6 - Reserved value

ISDN Se3/0:15: RX <- STATUS pd = 8  callref = 0x1A52
    Cause i = 0x81E41E - Invalid information element contents
    Call State i = 0x03

ISDN Se3/0:15: TX -> RELEASE pd = 8  callref = 0x9A52
    Cause i = 0x80E5 - Message not compatible with call state
    ISDN Se3/0:15: RX <- RELEASE_COMP pd = 8  callref = 0x1A52

I suppose that the router make  decision to send  Release but base on information which it is received in status message.
This kind status message appears every time  when router sends PROGRESS IND i=0x81B6.
I tried to find what Progress Ind i = 0x81B6 - Reserved value  means but without successful. Do you know it?.
I ask  because sometimes the connection is working and I noticed that in setup there is not  Progress Ind i = 0x81B6 - Reserved value . 
Maybe IF I know what this value means I will be able to find solution my problem.

Thanks
Rico.