Hi All, We have made numerous improvements to build 5.1 4128 which are available in the form of updates. You can download these updates by running the 'Check for updates' tool in the 3CX Phone System program group. (Note NOT from the web interface but from the separate executable in the 3CX Program group on the 3CX Phone System machine) Below you can find the exact fixes included, however this update resolves issues in relation to 'Stuck' calls, VOIP provider registration, IVR and more. Fix: route for out of dialog MWI notifications sent through the tunnel. Fix: IVR can transfer calls if port of PBX is not default (5060). Fix: VOIP line re-registration procedure in case of network failure of voip provider is inaccessible. Fix: update of VoIP lines configuration and updating registration status after changing the line configuration. (line remained registered if both directions are disabled from Web interface). Fix: PBX now drops a call if server leg(UAS on PBX) doesn't receive ACK from remote party (UAC). Previously it continued to handle unestablished call. Fix: NIC with network mask=0 uses STUN. localSubnets option with value 0.0.0.0/0 interpreted as all addresses are local. Fix: for deadlock in PBX. timeOut implementation for route and target is changed. Fix: Fixed length of tiff image stream in pdf-file. Fix: Fixed PDF object containing PDF parameters. Fix: Memory leak in media server. Fix: Memory leak in IVR Server. Fix: Crash in IVR Server. Fix: Prologue/epilogue is added to IVR signaling functions to prevent unexpected PBX termination in case of exceptions. Fix: Attended transfer functionality (prevent execution UAS related code on UAC leg). IMPORTANT NOTE! The updating process runs a VBscript to complete the update process. Many anti virus software do not allow this script to be run. If you are running anti virus software on the machine of 3CX Phone System, please add update.4287.vbs" into exception check/scan list and temporarily stop its script scan. We look forward to your feedback!