More RepRapDiscount/LCD Repetier issues?

Well, issue. This one doesn't seem to fit any of the 'standard' problems, and I'm scratching my head.

Extrude forward, all is good with the world.

Retract? LCD goes bonkers. Motor skips steps. LCD stays bonkers -- until I extrude again.

This is insanely repeatable.

I tried slowing down the UI_DELAYPERCHARACTER from 320 to 500 in ui.h, in hopes of it just being noise. I'm using the short cables with the LCD, unshielded.

Anyone?

I did notice that the pins for extruder drive are:

#define E0_STEP_PIN 26
#define E0_DIR_PIN 28
#define E0_ENABLE_PIN 24

and the data pins for the display are:
#define UI_DISPLAY_D0_PIN 23
#define UI_DISPLAY_D1_PIN 25
#define UI_DISPLAY_D2_PIN 27
#define UI_DISPLAY_D3_PIN 29

Physically close -- I'm wondering if I have a crappier than usual RAMPS knockoff.

I'm contemplating swapping the pins out for E0/E1, moving the driver and connections, and seeing if the problem disappears.

Just noticed that it only take a 1mm retract to bug out the display. Any other motor move (X,Y,Z, E+) brings the display back to life.

Very strange. I need to tear this thing apart. I'm guessing solder bridge or something related to the extruder 1 direction pin.

Sure enough. Still not sure what the problem is, but swapping E0 to E1 resolved it. Next time I'm in a dismantling mood, I'll take a look at the electronics.

Or not. If it works, why fix it?