Beersmith- water calculation problems

I brewed an IPA on Monday and had issues with my water volumes post mash and post boil. In both instances I was very low. I have not had this issue in the past.

Used the Northern Brewer Dead Ringer IPA recipe. All grain.
12 Lbs of malt

I use a 10 gallon Igloo cooler for my mash tun and have had pretty good luck with mashing in the past.

Going off of memory:

15 qts of water for mash
Batch sparge in two steps (0.54 and 2.85)

After my sparge was complete I was about 1.5 gallons short and after the boil I had to top off with another 1 gallon.

Could this be a calculation error on Beersmiths side or most likely a mash issue?

Thanks in advance for any help

check for correct grain absorption rates, check the include dead space in calc box and make sure it is correct for your setup. Post boil, check that the numbers it's using accurately reflect your experiences with boil-off rate and loss to trub.

BS can get pretty close, but only if you enter accurate numbers based on your actual setup and experiences.

If it's something that you haven't had happen before...maybe it was a simple measurement error with water additions?

It does sound like the total water you used is too low, at about 7G, you would lose some to the grain, dead space, and trub, with 7G in the mash, i'd expect to get 5.5G +- a quart into the boil pot. which would give you about 4G into the fermenter.

make sure in your equipment profile that your top-off water (both pre-boil and/or into fermenter) are 0.00