This seems to be an ongoing issue that is getting "resolved" but some similar issue continues.

I have had the lead breaking allowing the Mob to wander but the knot remains. The knot can then be clicked off and then disappears. If I have returned to the area soon enough the lead will be on the ground nearby. If I fail to notice the lead will of course despawn. 

This was first noticed with my horses at my base if the chunk is unloaded the issue will occur but not every time. As long as I am near by the leads do their job. This happed to me yesterday April 19 2023 in the nether with a frog. I had two frogs attached to one fence left the area about 300m away left the nether then returned. One frog was still leashed ( tied up) the other was not. I do not recall if the lead had despawned of not.

I will endeavor to track distance and time but quite frankly if a mob is cross chunk boarder or in an unloaded chunk this should not happen. 

Thanks