I think as well that the changed pulseaudio service-file has no effect. It occurred several times since then. Once even 5 reboots where necessary to fix the issue. In the journals there are several interesting lines, especially the last 4 ones:
Dec 20 14:34:08 Sailfish telepathy-ring[4151]: trying to create call to "+XXX"
Dec 20 14:34:08 Sailfish ofonod[3045]: dialing "+XXX"
Dec 20 14:34:08 Sailfish kernel: binder: 3045:26274 got transaction with out-of-order buffer fixup
Dec 20 14:34:08 Sailfish kernel: binder: 3045:26274 --> 6528:0 transaction failed 29201/-22, size 284-48 line 2442
Dec 20 14:34:08 Sailfish mce[2872]: tklock.c: tklock_datapipe_uiexception_type_cb(): uiexception_type = none -> call
Dec 20 14:34:08 Sailfish telepathy-ring[4151]: call create request to "+XXX" successful
Dec 20 14:34:08 Sailfish kernel: binder: 3045:26274 got transaction with out-of-order buffer fixup
Dec 20 14:34:08 Sailfish kernel: binder: 3045:26274 --> 6528:0 transaction failed 29201/-22, size 284-48 line 2442
Dec 20 14:34:08 Sailfish kernel: send_afe_cal_type cal_block not found!!
Dec 20 14:34:08 Sailfish [4158]: [D] unknown:0 - Type: "org.freedesktop.Telepathy.Channel.Type.StreamedMedia"
Dec 20 14:34:08 Sailfish [4158]: [D] unknown:0 - Interfaces: ("org.freedesktop.Telepathy.Channel.Interface.DTMF", "org.freedesktop.Telepathy.Channel.Interface.Hold", "org.freedesktop.Telepathy.Channel.Interface.Group", "org.freedesktop.Telepathy.Channel.Interface.CallState", "org.freedesktop.Telepathy.Channel.Interface.ServicePoint", "org.freedesktop.Telepathy.Channel.Interface.Splittable.DRAFT")
Dec 20 14:34:08 Sailfish lipstick[4404]: [D] onDestruction:267 - coverActionIndicators destroyed voicecall-ui.desktop
Dec 20 14:34:08 Sailfish lipstick[4404]: [D] onCompleted:263 - coverActionIndicators created voicecall-ui.desktop
Dec 20 14:34:08 Sailfish kernel: HTB: quantum of class 10010 is big. Consider r2q change.
Dec 20 14:34:08 Sailfish kernel: qdsp_cvp_callback: cmd = 0x13198 returned error = 0x1
Dec 20 14:34:08 Sailfish kernel: voice_send_cvp_topology_commit_cmd: DSP returned error[ADSP_EFAILED]
Dec 20 14:34:08 Sailfish kernel: voice_setup_vocproc: Set topology commit failed err:-131
Dec 20 14:34:08 Sailfish kernel: setup voice failed
I’m happy to provide the complete logs to the developers but not publicly. These logs are from a XA2 Plus Dual SIM with SFOS 3.3.