I swear I’m not doing something wrong, but I’ve only done this 2-3 times, so I want to shoot the messenger. The scenario: you type in something, fumble some keystroke reaching for ctrl-z and suddenly you can’t undo the last change, but you can undo the changes before that. It’s as though you type:
…and then expect crtl-z to undo the ‘3’ first, but it does the ‘2’, and then the ‘1’, leaving the ‘3’ there. Like I say, there’s a key combination, or maybe just a random occurance, where the most recent edit can’t be undo’d. The last time I did it, I accidently turned on stream block marking, so I thought it had something to do with that, but I can’t repeat the behavour.
What version are you using? I tested on ME2006 and 2008 and did not get anything like that. If I type 123 and then trigger undo in any fashion, all 3 characters are removed upon the 1st undo command. Are you using the standard key map? What is the file extension?