I was undoing the blocks and I think i did it too fast but im not sure because i tried to replicate it but couldn't
I just happens from time to time
This is a known bug with undo and redo. The best way to avoid this, is just by not using them.
I think that's a little extreme. Undo can save you a ton of time if you've deleted a long script!
Ok, in that case, then yes, but for little things like blocks getting dropped in the wrong slot, there's not a real need to do it, unless you drop it in a slot that has a bunch of text.
I revise what I said, it should only be used when absolutely nessecary.
:~)
Undo is okay,but redo isn't