Craig said:

During the summer and fall, a couple of my butternut squash
developed splits in the them,
Most of the splits were around the top near about 2" below the stem,
Other splits also happened vertically up and down the squash.

Most of the butternut squash did fine though.

What would have caused this ?

Could be the sun, most likely to occur if foliage has been lost to mildew,
exposing the fruit. Some varieties are more likely to crack than others.

--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)