Provisional response (malformed)

[complex1]

Hi,

Please can somebody explain why this message always occur in the Server Activity Log on an incoming call to this external extension?

Provisional response (malformed) arrived to Leg L:xxx.2[Extn]

The extension is a PAP2T-EU ATA, provision is switched off in 3CX as in the ATA and located outside the LAN. The ATA is set up manually.
In and outgoing calls goes without problems.

Thanks.