Leviton Dimmer 3 way remote switch only turning off
As you seem to know, the "bare" wires, along with any green or yellow/green wires, are always and only Equipment Safety Ground. They get used for nothing else.

How the 3 wires must be allocated

NEC 110.3(B) requires you install the light switches according to the instructions.  This is not optional.  Since Reading the Fine Manual is mandatory, you see the "3-way configuration" diagram plainly shows 3 wires (other than ground).  Two of their uses are obvious. The third appears to be some sort of communication wire that runs only between the units.   So, in the /3 cable between switches, we must allocate the wires as follows: 


White MUST be neutral.  (NEC 210.something) and it always connects to the WH (silver) terminal on both smart switches. (It also goes onward to the lamp).  That's done! 
Always/line/supply hot traverses the /3 cable. The conventional color for that is black, so let's stick to that. This goes to the BK terminals on both smart switches. Done and dusted.  We will not revisit this again. 
The remaining wire (shown in the instruction as a thru-wire) is Yellow/Red and is the communications wire that runs only between the switches.  The only wire we have left to allocate is the Red wire in the /3, so that is that.  It connects to the YL/RD terminal of each smart switch.   I am super fond of yellow tape for travelers, and while this isn't a traditional traveler, its code is yellow-red, so it's too perfect to resist marking with a yellow band! 


We have now assigned all the wires in the /3 cable.  Pretty straightforward once you figure out which wires are needed, assign tasks to the wires in the wall, and color-code them for purpose. 

One last wire to connect: the hot wire to the lamp, which is switched-hot.  That wire could be re-marked red, which is the conventional color for switched-hot.  That goes to RD wire on the master dimmer.  Piece of cake! 





Wait a minute! The RD terminal is in one box, and the wire's in the other!

Because the smart switches are not in the right boxes. Switch them.