I have a new system running 10 with latest Sp's. We use nexvortex sip trunking service on this system . The problem occurs when the customer parks a call and the caller hangs up while on hold. The BLF on the phone shows to still be busy. If the customer presses the BLF to retrieve the call they just hear the on hold music. When they hang up the park line is clear. We use the Cisco SPA 525 G2's. I cant decide if its 3cx that doesnt see the call disconnect...or if its the phone not getting an update from 3cx that the line is free.