i have a mashup (everything is set to responsive insede it) that has a pareto chart inside it and when i click "view mashup" everything looks fine. When i place this mashup inside a master (also everything is responsive in there) only the pareto chart doesn't scale in it. I tried with other widgets, like line chart and bar chart and they are working fine. I'm uploading some screenshots.
I can reproduce this issue you mentioned in TWX 9.1.0. I also didn't find any ticket to report this issue. If you can submit a PTC technical support case, I suggest you'd better do that for fixing.
I wasn't able to find a case for the issue you reported. Please let me know if you would like me to create one on your behalf.