Voltage colors not centered on charges

[brroberts1231]

For phetsims/qa#37

Windows 7, Chrome Version 61.0.3163.79 (Official Build) (64-bit), Does not occur on IE or Firefox.
This seems similar to something we've seen before, but I can't find the old closed issue.

Problem description: Voltage colors are not being placed correctly around the charges under some certain circumstances. Sensors and equipotential lines don't treat the colored areas as actual charged areas, they react to the actual charges normally.
Also, dragging the charges around when this happens creates new spots of color, where they were. (Difficult for me to explain in words, see the 2nd gif below.)The odd thing is, I'm only seeing this on my personal Win 7 laptop, but not on Bates, so @BryceAG suggested it could somehow be hardware related.

Procedure:

1. Open the sim in any wrapper (I tried Simulation, Events: Recording, and Mirror inputs, they all showed the same problem. Once I spend more time, I'll check that it happens on all the others too.)
2. Drag two charges onto the screen. (Doesn't seem to do it when you only drag one out.)
3. Check Voltage
4. The voltage fields shown are not centered on the charges.
5. Pressing Reset All, then checking Voltage again may show some colors without any charges being placed at all. The sensors and equipotential sensor will correctly show 0V. Only refreshing lets me restart without some color floating around.

Or, if you don't reset, and you drag around the charges, you'll see what happens in the 2nd gif.

Screenshots:

[ariel-phet]

#106 may be related