My wife's had this for years. She asked her doctor, who diagnosed them as idiopathic cramps. So far every doctor friend we've asked made the same diagnosis.

She gets best results from MORE EXERCISE! please. She also wears compression socks when off the bike. She likes 2XU, Vitalsox, and Blitzu best. Also taking a 500/250 cal/mag pill and 200 mg potassium after exercise helped. If it's cramps, 30 one-legged calf raises on a stair, full range of motion, every other day. Plus all the rest of it.

Cramps basically give you DOMS. Hit those calves as soon as possible.