I can confirm this. Using a silk touch pick with unbreaking on it will not allow you to break an enderchest. However, silk touch with no unbreaking would break the enderchest. Not sure if this is a MC bug or a plugin issue.

 

I am also having the same issue, with both my ef4/un3/silk & my ef4/silk picks.
Regretfully I cannot try this in single player, since I've got nothing but ECC as my Minecraft fix of choice.

 

Same.

 

Has anyone tried this on single player at all?

 

It is not a mc bug I broke an enderchest with an eff5 unb3 silk1 however
It did not break until I broke it from beneath

 

That makes it a minecraft bug... :|

 

same thing hapened to me with a crafting table, i was mining it with an EFF4 diamond pick (not very smart) and it would not break, turns out i was mining it to fast, it worked fine when i did it with my fist tho. i dont know what else to tell you.

 

In Single Player, I broke an Ender Chest with a Silk, Eff 4, with no problems at all

 

its hapening to me alot recently, sometimes i have to break obsidian up to 10 times before it drops, its very annoying.

 

That's just lag, not a bug. This is called a "rubber-banding" effect and is caused during peak hours with high lag.

 

Thats what i thought, but i tried to break it with a regular diamond pick instead of an efficiency 4 and it worked perfectly fine.