All of the above.
It's also about Grady's mismanagement of the whole dispute. Some of the stronger unions - for obvious reasons - are in the Post-92 sector, many of whom are not USS members, and who consistently voted 'yes' in the disaggregated ballots. They took huge hits in their pay packets whilst other USS affiliated institutions didn't meet the 50% threshold - in essence, they were taking on this fight for them and bearing the consequences of that.
Meantime once Grady makes headway on the pensions dispute - the only thing she apparently cares about - she wants the whole lot resolved. Post-92 say 'hang on, we've achieved NOTHING out of this and sacrificed the most. You are not throwing us under the bus'.
Hence the fury when she stood down strike action in March, effectively undermining the strength of her own position.
It should never have been four fights: the USS dispute should have been kept separate and the main one a simple matter of pay and conditions. Not being clear about precisely what we are asking for has muddied the waters and, probably, the negotiations.
And the ballots should all have been aggregated.
Grady has walked us into this. As General Secretary, she's unfit for post.