The motors are deliberately held energised, as you say this is to keep the position locked. The motor current should be quite low and the motors should not get hot. However some batches of this type of motor seem to draw a lot more current and some can get very hot indeed. There are other threads here with more discussion of problem motors. Keyboard shortcuts and motor temperature - Request Help - OpenFlexure Forum , An absolute position encoder for the Openflexure Microscope - Contributions - OpenFlexure Forum, How to configure/use sangaboard? - Request Help - OpenFlexure Forum.
My motors barely get warm, so it sounds as though yours are hotter, but not at the really hot end of the range.