Insertion and removal of filters on the non-xfade backend is not robust (using trunk) in several ways:
* insertion while playing will stop playback. Playback will start again if asking to play a new song.
* removal while playing or while playback is paused will hang RB completely.

I used the python console with the simple code:
import gst
a = gst.element_factory_make ("volume");
shell.props.shell_player.props.player.add_filter(a)
b = gst.element_factory_make ("audioinvert");
shell.props.shell_player.props.player.add_filter(b)

and also experienced such problems while working on #76522.