What operating system are you using?
Yours are not typical experiences at all, so something is very much up on your machine.
Although Macs with Retina displays are notorious for this kind of buggy behavior.
PC (HP Pavilion dv7), 8GB RAM, Win7.
I do have various languages enabled (Japanese, Chinese Taiwan, Chinese PRC, English), and the shortcut key for switching among them is Shift-Alt (also used for nudging clips on timeline), but this does not seem to be the issue. (As long as you take some action within PE12 after pushing Shift-Alt, the language setting will not change.) I have tested with various languages activated and could not replicate the problem.
I know that with some of these things there is either a combination of actions that the program doesn't like, or the user hits some key by mistake that triggers some part of the program. I was hoping that if it was one of these, that someone might have had the same problem. (This is how I learned about the issue of language keyboards.)
I have disabled the language keyboards to see if this was the problem. If it was, it's a bug, since PE12 is capable of generating beautiful titles in Japanese. Seems odd to design a program to do this, when enabling the Japanese input causes problems with the program. (According to several online posts, it does.)
I disabled all FL keyboards. This did not end the problem.
Problem seems much more likely to occur when "lassoing" large blocks of clips.
Message was edited by: Kawika808 - added clarification