I have complained about this a couple of times, in at least one thread - I thought on this forum, but I can't seem to locate it in a hurry now. In short, since a recent update of PMail, probably the one to 4.41 or to 4.50 beta, some change was made to the editor which produced symptoms which sound rather like yours. In my case, what I noticed - and still do moderately often in version 4.51 - is this. You start on a message, then need to go back and modify what you have already written, e.g. by inserting some new material in an earlier sentence. In those circumstances, you often find that the insertion point has jumped away from where you were sure you had placed it. I'm a fast typist, but not a touch typist, so I type away, then find I have garbled the message by inserting my extra material in the middle of a word. It's a shock and an annoyance every time. The actual insertion point is usually close to where it should be, I think always on the same line, but it has moved, without warning and for no discernible reason.