Absorption, hand't thought of that.
I believe it is because I let the bag drain over time. In the Rubbermaid cooler with graduated markings, I net at least 1 gallon of wort > 1.040. I hate to let this go.
My options are too discard, toss it in the kettle & boil longer, or boil it on the stove & concentrate it into a sticky goo. It adds a few points to the gravity at such a high concentration.
In BS, I adjusted the mash absorption from .96 to .568 to match the BIAB absorption and it brought the water requirements down about a gallon - just as the BIAB mash profile did.
Since this is only MIAB, batch sparge occurs after draining the first runnings.
This just may work.