when a strider is in lava and turns to the warm texture the texture becomes missaligned from where it is usually placed, A cold strider has the correct texture this is the result of an attempted fix for
MC-176095

Edit: Cold striders with saddles show no texture change on top the that shows a saddle their faces have a stirrup pad dangling on their face TL;DR Misaligned and invisible saddle texture for cold striders