USING COMMAND "D" NO LONGER DUPLICATES ITEM OF FILE

[TriumphNut]

When trying to duplicate a file, using Comand "d"; rather that duplicating the file, it closes the document and gives me a new window. It's been working fine for nearly four years, suddenly started doing this.
Bought New: APPLE PRO TOWER Mid 2012, El Capitan OS10.11.4
Processor:3.2 GHz Quad-Core Intel Xeon,
RAM: 16 GB 1066 MHz DDR3 ECC,
Graphics Card: ATI Radeon HD 5770 1024 MB
Pulled the Key Caps and configured keyboard to Dvorak layout when NEW.
Don't recall, but it might have started doing this after I upgraded to the .4 version OS.
Been Using a Mac since 1986. Have converted every keyboard to DVORAK since my Mac Plus.
NOW TO duplicate, HAVE TO GO TO THE TOP WINDOW & choose "duplicate".

 

[honestone]

First, please do not use ALL CAPS, as it looks like you are shouting.

Secondly, Apple released V10.11.5 of El Capitan the other day. You can get the Combo Updater from here:

https://support.apple.com/kb/DL1876?locale=en_US

Third, what kind/brand/model keyboard are you using?