I have seen different genera of snakes biting themselves in extreme conditions.
Bothrops alternatus found dead and biting itself on a burned field, Liophis poecilogyrus biting itself, dying next day, also in Epicrates.
In the cases I observed, it was regretfully associated with death.
Looked like a neurological condition
However your case seems to be different since the snakes does feed and obviously is alive.

Best of lucks and I do hope to hear how this develops,
David