The Mini DisplayPort to VGA adapter firmware update fails to install on OS X El Capitan 10.11.6.

Firmware installation steps have been followed from About the Mini DisplayPort to VGA adapter firmware update - Apple Support

I have a mid-2012 Macbook Pro and wanted to install this firmware as a solution to the erratic connections and crashes I faced while connecting to external monitors or projectors using the Apple provided adapter.

1. Just before installation the error dialog shows

"This package is incompatible with this version of OS X and may fail to install."

It also provided options to "Cancel installation" or "Continue Anyways".

2. Continuing a forced installation eventually fails with warnings too !

Has this been solved or experienced by others? Any pointers, thanks in advance.