I was recently exploring the Nether on a snapshot survival world and got my hands on a saddle. I mounted a Strider and tried to get him on some soul sand to get across my cobblestone bridge. But then as I returned to the lava off of the soul sand, my Strider started to float, remain purple, and not be able to move up on top of a full-sized block like cobblestone or even return to the soul sand it was previously standing on. I attached some very laggy videos (I have an old mac lol) that shows the bug. I noticed that this does not happen with every Strider, but it does with striders who have been on soul sand for a while and Striders whose feet do not sink into the lava like most do. Hopefully, you can patch this in the next snapshot, or someone else with a better PC and recreates the bug video for another report.