I have a problem: if you add 2 or more measures in visualization and it will be a different type of data ( percent and sale for example) and you add a trend line in both of them when you change in select list (drop-down list) the trend position don't change and all data in line chart go down of chart about zero line.
If the line isn't changing even though you are filtering and can see the data change, you might have created REFERENCE lines instead of trend lines. Without seeing example that's just a wild guess.
I'm not a real big fan of mixed Axis charts especially if both are lines. Very difficult for end users to know for sure what they are seeing. I've used COMBO charts when the user insists on it so that one is a bar and the other is a line or the other is a dot inside the bar.