DR-2 is just the Drive Response Setting it is set at, choice of 3 settings. You need to push button on the left panel to display any fault code occurring.
There were 2 styles of left display panels used. 1st version the panel is light gray and has Light Button in upper left corner, this button also says "hold for codes". Push and hold a few seconds to display the fault code. 2nd version has an oval shaped display with an "I" Information button, push and release that button to toggle through various information at about 4th selection a code should come up if the is code present.
When it goes to 50% speed means whatever the problem is has caused controller to go into "Work Mode". You can use the Rabbit button to toggle the % speed up to 99% to get full travel speed.