Why does the memory script get stuck moving time to infinity?

[davidtaylor23]

When I try and test my memory chip, the memory runs perfectly fine until it reaches "while out <> 75 {
    tick, tock,     // tick, tock prevents hang if sync. parts used in KB path." where it proceeds to run through the clock to infinity.
I am very confused as to why this occurs?
Here is my memory implementation:
    DMux4Way(in=load, sel=address[13..14], a=rama, b=ramb, c=screen, d=keyboard);
    Or(a=rama, b=ramb, out=ram);
    RAM16K(in=in, load=ram, address=address[0..13], out=outram);
    Screen(in=in, load=screen, address=address[0..12], out=outscreen);
    Keyboard(out=outkeyboard);
    Mux4Way16(a=outram, b=outram, c=outscreen, d=outkeyboard, sel=address[13..14], out=out);