Yes, I just had a further look into the code - if the 'Maximum Payout Amount' field is set then will then send every transaction seperately instead of one larger 'sendmany' transaction.

I set this field on/around August 2, so I guess that explains it. I've unset the field, hopefully payments should return to what they were before.

Apologies, the yiimp code is sometimes not doing what the panels suggest it would do