L.A.
Are you adding water when the water gets low? If so it is because you are adding cold or room temperature water, it needs to be boiling water.
FYI, we never soak our pintos.. That will also cause the skins to break.
Instead, first bring your salted, seasoned water to a boil, then add the dried beans, let the water come to a boil second time and this time, partially cover the pot with a loose fitting lid, lower the heat and simmer for 2 hours.
IF you need to add water, add boiling water.