For what it's worth, this JSL clipped image issue just happened to me today. (Win10, JMP 12.2)
Issue: PNG chart images, saved from Bivariate charts, would clip off to the right and bottom maybe by 25% of the image size.
My PC had been in sleep mode before this issue surfaced, then after the PC reawakened and ran the JSL scripts this issue oddly occurred. So I did a PC reboot and issue resolved and I now get proper sized PNG images of the charts.