Did you try the .066 version which supposedly fixes the issue?
The .066 version was on Artsoft's website for years. It was only replaced when it stopped working in Windows 10, and CNC Router Parts created a patch for .062 to run in Windows 10. Artsoft basically abandoned Mach3 over 5 years ago.
The problem with Mach3 is that every version has different bugs. The reason they created Mach4, was because Mach3 got to the point where they couldn't fix bugs without introducing new ones.
Most of us here have switched to UCCNC because it's far superior to Mach3. And it's 1/3 the price.