Thank you for sending these files. I could see the "problem".
For the stock you don't see buy/sell signal, if you scroll towards left then you will see the signals on chart. So, most certainly it is the Trading System that is not generating signal for those duration that is visible on chart. Please confirm if you think there should be signals during that time as well.
Regarding dramatic change of scale. I see this problem but it is triggered by stocks like GUAR3, or HGLG11. Please allow me to explain.
When you change the stock in portfolio/watchlist view then it is NOT the default template that is used for new chart but an ad-hoc template is created from the previous chart and that is applied to new chart. It is done this way so that if you make any change in chart like resizing or adding any new indicator or any other change then that too is applied to new chart.
Now, in the case of GUAR3 or HGLG11, there isn't much data in last 6 months. You can check that by going to Quote Editor. When the stock with less data is selected then Stockalyze tries to show whatever little data is available into the full chart width and so the scale gets changed when such stock is selected. And since all chart parameters are applied to next stock you continue to see large scale even after selecting other stock.
I do see there is a problem but I will need to decide how exactly to fix it. I will take some time. In the meanwhile you can just apply the 6M zoom again when the scale is enlarged for the stock which has sufficient data.
Sorry for this lengthy explanation but I hope I have explained it clearly.
Thanks for reporting it. Any suggestion to improve would be welcome.