When you put a Strider on a lead and drag it somewhere, afterwards the Strider will refuse to move from the spot it is in. It will literally just stay there until the end of time.
That is until you pull out a Warped Fungus or drag it with a lead once more.
Steps to reproduce
Find a Strider hanging out in lava
Use a lead to drag it somewhere else
Notice how it doesn't move on it's own and never will, no matter how long you leave it for
I'm unable to reproduce this. I leash it, let it go, it stands around for a bit, and then walks somewhere again.