In some cases it causes the error like:
Error message "Интерфейс «(null)» для пути /org/mpris/MediaPlayer2 объекта не найден"
(for example deadbeef was affected). Suggested patch should fix this
issue and seems to be working with at least deadbeef and qmmp mpris
engines.
First of all it seems that freezes were caused by stuck dbus calls. I've
enabled dbus call timeout (build-configured, default to 3000 msec). And
moreover I've added one more thread lock for dbus calls.