Possibly Reaching Current Maximum for Arduino UNO 5V Output?

I'm doing some experimenting with LabVIEW and I have my UNO hooked up to an 8 bit shift register and a potentiometer. It's been able to do a full 0-1023 sweep before, but now that I have it outputting in binary the value inputted (such that at 0 all off, at 60 ish half on because it scales to 0=255, which ends up being 16...) anyway at maximum now it'll only do around 1000 +/- 5 but usually on the minus. Is it possible that I'm running into a limit on something?

I added an output toggle and when I disable the output the input shoots right back up to 1023, enabling again it drops down to around 1000. Is 8 LED's, a pot, and a shift register looking like my maximum?

(I'm using standard USB power from my computer, I don't think it's any more than the standard 500ma and I have no reason to believe it's not)

Measure 5v with DMM when you have a problem.

Show us a good schematic of your circuit.
Show us a good image of your wiring.
Give links to components.
Posting images:

I’m in the process of buying a DMM, it would be extremely helpful if I had one already though.

I took the pictures on my phone but the typing is easier on desktop so here’s an imgur album. Starts with my LabVIEW block diagram just in case you wanted to see it, then my wiring in 2 pictures (but it’s a jungle as you might imagine) then the schematic I followed minus the pot I added.

Link to shift register: http://www.ti.com/lit/ds/symlink/sn74hc595.pdf but the one in the picture on their website doesn’t match, only the number. Which is weird because it’s from the sparkfun website and it’s a sparkfun kit.

I checked the manual to see if there was a part number on the pot and there isn’t, all I can tell you is that it turns roughly 300 degrees total. Resistors are 330 ohm (if I put the right ones in, I just followed the colors). Breadboard is labeled as “standard solderless” and that’s it.