If one of the children of the bin fails state change, it is not sufficient to just remove it in order to restore clean state. From a quick glance at the gstbin.c, it looks like:

- when element's state change fails, all remaining children do not change state, so the bin may have some children in a changed state, and others in the old state,
- removing the child that failed statechange does not cause remaining children to transite to the previously requested state,
- removing the child that failed statechange does not restore bin's last state change return to a proper value - it's still an error,
- removing a child that posted async-start, if all other children have already posted async-done, will not cause the bin to post async-done if last state change return is error (even if the element that errored was already removed from the bin).

The simple workaround is to call again gst_element_set_state() on the bin after I remove the child that failed state change.