Refer to gstreamer/gst/gstevent.h, where all CUSTOM event types have a GstEventType >= (270 << 8).  This always results in values greater than 2^16, yet we see from gst-plugins-bad/gst/gdp/dataprotocol.c that gst_dp_event_from_packet_1_0() reads the GstEventType using GST_DP_HEADER_PAYLOAD_TYPE(), which is defined as GST_READ_UINT16_BE().  Consequently, any GST_EVENT_CUSTOM will deserialize with a bad type.

I'm not very familiar with dataprotocol, but it's not clear to me how this can be resolved without incrementing the dataprotocol version.

In future revisions of the protocol, I would suggest that serialization of any enums support values up to 32-bits.