> Be test subject 4509
> Place a cube in the present
> Go to the future
> 20-year-old cube is in that position in the future
> Take 20-year-old cube back to the present, leave it somewhere
> Expect to see 40-year-old cube in that position in the future
> There is no 40-year-old cube
> Have an existential crisis because the future cube's current destiny of being in that place 20 years from now has somehow not been fulfilled

Have you ever seen/heard of/read the wikipedia page about Logan's Run?

The main premise of that was about someone trying to escape a dystopian society where everyone gets killed at a certain age (21 in the book, 30 in the film adaptation).

Now, what does this have to do with anything?

Well, consider how, whenever you attempt to respawn a cube, the previous cube you had automatically gets fizzled, without any external thing needing to come in and dispose of it. This heavily implies that there's an internal auto-fizzle mechanism within the cubes themselves.

And now, consider this: If one has way too many cubes, and has the means of automatically disposing of a cube, would it not make sense to automate disposing of abandoned cubes (such as if a cube falls out of a test chamber), rather than having to clean up the inevitable flood of cubes later on down the line manually?

And now, back to why I mentioned Logan's Run earlier on.

Suppose we have a cube (C) in the present (T0). We place it somewhere in the present (present cube is C0), and leave it alone for 20 years. 20 years later (T20), we grab that 20-year-old cube (C20), and take Cube C20 back in time by 20 years (to T0). However, Cube C20 is still 20 years old, despite being taken back in time by 20 years (as we had to abandon Cube C0 for 20 years before it became C20, which we took back in time). Now, we leave Cube C20 alone in the present (T0), and observe it again 20 years in the future (T20) - at which point, it should now be 40 years old (C40), and presumably having a mid-life crisis.

HOWEVER!

If the cube's auto-fizzler was set up to, say, automatically fizzle any 30-year-old (or 21-year-old) cubes... THE CUBE WILL NEVER BE 40!

Or, in practical terms...

A future cube (C20) which you take to the present (T0) will not be available in the future (T20), because it would have died of old age in the meantime.

Meaning that you can only have the present version of the cube (C0), the 20-year-old future version of that same cube (C20), but no other instances of that cube may exist.

fine here it is in image form instead

please get out of my house