I have this issue where the image used for the progressbar track is being stretched (for 125% Windows scale but issue also occurs on 150% scale) in an undesireable way.
Now I have to admit I do not understand the way the stretchY1 and stretchX1 parameters work, but both are set to value 7 (copied from existing bitmap skin, using same image dimensions). Changing this value does not seem to have any effect for me.
I do provide 100% 150% and 200% variants of the progressbar track image.
Top is the erroneous result, bottom is what is desired: