Quote from Spunky:
Like I said, I do not have the problem that you are having. I can change the zoom all day and the trendline stays the same. I suppose that I could intentionally play around with the Snap to price % threshold setting and change the scale to arithmetic or logarithmic depending on whether I use straight lines or hi and lo points and get something that resembles what you are showing. Any charting software worth its salt would have those options and do the same.
Obviously you have a lot to learn about charting as you have the problem and cannot fix it. It is not Amibroker. Look in the mirror.