cramps are actually caused by central sensitisation of the nervous system. this means that there is a problem at the nerve root and this increases the sensitivity of the nerve to stimulus such as pressure stretch or summation. this means that a normal normal contration, stretch or pressure on the muscle will elicit a cramp.

i would check your thoracolumbar joints starting at T10 worki9ng your way down to L5 you will find joints that are stiff and painful that you didn;t know about mobilise them and your cramps will disappear.