Error bands in Graph Builder - sometimes wide, sometimes thin?

[#1]

Any idea why some of the error bands are wide, and some are thin lines? It might be all wide, or all thin - I can't understand what it depends on and how to control it. Any ideas?

[#2]

It's hard to say from the image alone. Could you upload the data (anonymized), or replicate the issue on a sample dataset? 

Or, could you include a screenshot of the "Control Panel" area of the Graph Builder window (Red Triangle -> Show Control Panel). 

Based on the image, my guess is that the Error Interval option is set to Band for the blue and red data, but Error Bar for the green data. It's also possible that Two-Way Intervals is active unintentionally. I recommend to check the settings of Error Interval and Interval Style, and we can continue from there.