(lt-executable:31946): GStreamer-CRITICAL **: gst_element_link_pads_filtered: assertion `GST_IS_ELEMENT (dest)' failed

(lt-executable:31946): GStreamer-CRITICAL **: gst_element_link_pads_filtered: assertion `GST_IS_ELEMENT (src)' failed

(lt-executable:31946): GStreamer-CRITICAL **: gst_element_link_many: assertion `GST_IS_ELEMENT (element_2)' failed

** (lt-executable:31946): WARNING **: Failed to link elements (step #4)