manipulate - Strange evaluating indication of output cells

Something like this happened when I was working with two Manipulate cells. I saved the notebook, duplicated it and only keep these two cells, and opened the notebook with a fresh kernel, it still happened immediately (in trusted directory, if not, this happens after clicking enable dynamics).

I have repeated this on Mathematica 10.1 on OS X 10.10.3 and Windows 8.1 (I am not able to open it in version 9).

So is it a bug, or an expected behaviour I am unaware of?

The code in the notebook is here:

First Cell:

Manipulate[
circle = ParametricPlot3D[{Sin[x], Cos[x], 0}, {x, -Pi, Pi}, 
PerformanceGoal -> "Quality"];
circle1 = First[circle];
circlebase = Scale[circle1, {1, 1, 1}, {0, 0, 0}];
fin = Table[
Translate[Rotate[{Point[{-1, 0, 0}]}, - i 4 Pi/1000, {0, 0, 1}], 
 2 {Sin[i 2 Pi/1000], Cos[i 2 Pi/1000], 0}], {i, step}];
circlerolled = 
Translate[circle1, 

2 {Sin[ 2 Pi step/1000], Cos[ 2 Pi step/1000], 0}]; 
Graphics3D[{fin, circlebase, circlerolled}, 
PlotRange -> {{-3.1, 3.1}, {-3.1, 3.1}, {-0.1, 0.1}}, 
ViewPoint -> {0, 0, 1}, Boxed -> False],
{step, 1, 1000}]

Second Cell:

Manipulate[
circle = ParametricPlot3D[{Sin[x], Cos[x], 0}, {x, -Pi, Pi}, 
PerformanceGoal -> "Quality"];

circle1 = First[circle];
circlebase = Scale[circle1, {-3, -3, -3}, {0, 0, 0}];
fin = Table[
Translate[
Rotate[Point[{-1, 0, 0}], - i 2 Pi/(251/(-2)), {0, 0, 1}], 
 -2 {Sin[i 2 Pi/251], Cos[i 2 Pi/251], 0}], {i, step}];
circlerolled = 
Translate[
circle1, (-3 + 1) {Sin[ 2 Pi step/251], Cos[ 2 Pi step/251], 0}]; 
Graphics3D[{fin, circlebase, circlerolled}, 

PlotRange -> {{-3, 3}, {-3, 3}, {-0.1, 0.1}}, 
ViewPoint -> {0, 0, 1}, Boxed -> False],
{step, 1, 251}]

The code itself should produce this after executing them separately.If you are not able to produce it, you may try to download my sample notebook.

https://drive.google.com/file/d/0B6gQp_HcIW0ZVmwyeUJHR0MtM0U/view?usp=sharing

I guarantee it is not malicious (anyway you can open it with a text editor and see the source code)

Answer

This infinite evaluation is the result of "cross-linking" the two Dynamic expressions due to the failure to localize your Symbols with DynamicModule, e.g.:

DynamicModule[{circle, circle1, circlebase, fin, circlerolled},

 Manipulate[
  circle = ParametricPlot3D[{Sin[x], Cos[x], 0}, {x, -Pi, Pi}, 
    PerformanceGoal -> "Quality"];
  circle1 = First[circle];
  circlebase = Scale[circle1, {1, 1, 1}, {0, 0, 0}];
  fin = Table[
    Translate[Rotate[{Point[{-1, 0, 0}]}, -i 4 Pi/1000, {0, 0, 1}], 
     2 {Sin[i 2 Pi/1000], Cos[i 2 Pi/1000], 0}], {i, step}];
  circlerolled = Translate[circle1, 2 {Sin[2 Pi step/1000], Cos[2 Pi step/1000], 0}];
  Graphics3D[{fin, circlebase, circlerolled}, 

   PlotRange -> {{-3.1, 3.1}, {-3.1, 3.1}, {-0.1, 0.1}}, ViewPoint -> {0, 0, 1}, 
   Boxed -> False], {step, 1, 1000}
 ]
]

• 
  

  step is automatically localized by Manipulate and does not need to be added to the DynamicModule specification.

  
  


• 
  
  

  This localization should be included for all Manipulate expressions unless you have specific need to access the values globally, and if you do you will need unique Symbol names.