Question: Anyone have the problem with Undo operation (Cmd + Z) in Xcode?
When I am edit my Objective-C code with Undo operation, some symbols are not correctly edited.
For instance:
was {   

with Undo {{   

XCode 4.2.1

Answer: 
I have Xcode 4.3.2, which still has severe problems with undo/redo -- it will usually crash after one or two redo! Just before it crashes, it will usually do some nonsense edit.

---

*Added*:

I have experimented with the tip by Walt to turn off line numbers. However, I have not seen any significant drop in crash frequency. However, going slowly seems to at least reduce the crash frequency, but it is absolutely no guarantee -- it may crash even after an extremely simply small undo.

(I usually get anywhere from 1 to a dozen crashes a day, but since I try to avoid undo, especially several consecutive undo, the crash frequency has dropped somewhat.)

A crash may come on either undo or redo, with a slightly higher crash frequency for redo. Sometimes the crash comes after just a simple paste with no preceding undo/redo.

I have also experimented with changing font scheme to a very simple one, but it does not help.

My only tip would be: when you see that e.g a paste, or entered text, is inserted at the wrong place, try to save (or ignore that step), then chose Revert Document. Sometimes that trick works, sometimes not (and if not, it will crash). Sometimes it has helped by switching to another file and then back.

Also, if you want to undo just to inspect what the previous thing was, save before the undo, then, rather than redo, it may be slightly safer to Revert Document (but it is by no means any guarantee).

After a refactor, the window's fonts often look garbled. In this case, it has always helped to switch to another file and then back.

Hmm, is this Apple Quality? Steve's adherence to perfection?
they fixed this partially in Xcode 4.3.1, it doesn't occur that often anymore