Multiple bugs involving leads/leashes and dropped item visibility

After an unknown amount of time wolves in the "sit" position with leads attached to fences will lose their leads after what seems to be a not short, but within 24-hour period. Leash sprite on fences is gone; typically upon logging off and logging back in to a server, or even on simply reloading the chunk, the sprite showing the visible leash "wire" attaching the two entities is gone. One or two times I have been able to pick up the dropped lead on the ground, but this has been a random occurrence not helped by a second bug where blocks and other items dropped as entities are occasionally invisible. I cannot elucidate why the dropped leashes may be invisible, but when mining blocks it appears that blocks that do not quite seem "destined" to go into my inventory (by their trajectory as a drop) will not be visible as entities but will still be able to picked up, while items that will very much certainly go into my inventory are invisible