vā gets the augment juk (j) before the affix ṇi when the Causative has the sense of 'shaking'.,
As पक्षेणोपवाजयति ॥ But आ वापयति केशान् when the sense is not that of shaking. This form could have been obtained from the root वज् 'to move\, (Bhuadi 271) with the affix णि in the ordinary way without any augment. The special augment ज् to वा indicates that this root will not take युक्, which it would have otherwise done by the last sutra. The root वा belongs to Bhuadi 969(ओवै शोषणे) ॥,