Can't use relative path for frameworkOverride

Windows 8.1 also Windows 7

SA 3.1 1934

Custom Framework Path

If I try and put in a custom framework using a relative path, it clears it as if it's an invalid path. If I open command prompt and do a cd it switches to the path fine. So the relative path is correct.

The path works fine if I browse to it - but need to use relative path as it's a shared project.

Can't use relative path for frameworkOverride