Not sure if people are aware that on some occasions MT4 can be missing chunks of data that effects accuracy of trend lines. For people who don’t know you may expect support or resistance at a trend line you draw but if it is not accurate the support or resistance may be in the wrong place for your trade. If you want accurate trend lines you should get professional charting software like MetaStock Xenith. Then check your MT4 trend lines are correct before trading.
It seems to be a feature of some charting software that user-drawn trendlines change position if you switch time-frames.