Why are you still posting about this. An add-on is causing the problem.
If you build on someones brick without there full trust and hit command+z it will not allow you to remove your own brick.
This is by design.
Why? I remember you saying something about it, wasn't it that you could just undo a brick that the other player built a lot on, then that would all be destroyed? If so, it would be nice if you would add checks for things like that.
You could build a baseplate, wait for someone to build a huge thing on top of it then undo it destroying their stuff when you only have build trust. Previously it was not possible to check if would cause a chain reaction, but now it is so I will probably fix this.
If you start uploading a save, and have the chat bar open before it starts, you can't chat at all, or use scroll.
Just putting that out there, as it was not replied to.