My advice, as a long-time student of SN Goenka, is not to worry about it. There is a tendency among some students to chase certain experiences which is not the point of practice. Any craving for this or that attainment becomes a barrier for its attainment. Concentrate on observing whatever arises as it arises. I haven't seen Bhangha-nana in the suttas but it is described in Vism and, to my knowledge, in the Abhidhamma (see Bhikkhu Bodhi's Comprehensive Manual of the Abhdihamma). Also see Mahasi Sayadaw's 'progress of insight'.
All the very best with your practice.
“No lists of things to be done. The day providential to itself. The hour. There is no later. This is later. All things of grace and beauty such that one holds them to one's heart have a common provenance in pain. Their birth in grief and ashes.”
- Cormac McCarthy, The Road
Learn this from the waters:
in mountain clefts and chasms,
loud gush the streamlets,
but great rivers flow silently.
- Sutta Nipata 3.725Compassionate Hands Foundation
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