Reported here: Bug 384095
Default screengrab profile "X264 mute" works fine.
But screengrab profile "X264 with audio" does not work.
I found out possible bug - typo in options
(in file /usr/share/kdenlive/encodingprofiles.rc)
Default options for profile with audio:
X264 with audio=-i pulse (...)
But audio start recording with:
X264 with audio=-f pulse -i default (...)