My speculated reason for the sudden ending of take 5 is this:

(This is only spectaculation. I read the album as a story)
As Hikki mentioned in the SSTV interview, the album deals with Death. So my guess is that the sudden ending means Death and possibly a sudden one.

As I am open to any views on life after death. One of the beliefs I have is reincarnation.

So, the end of take 5 signifies the end of an individual's life. and his spirit reincarnates and takes a different form.
i.e. it become a child again and lives on earth as we can see from boku wa kuma. Then we follow this individual as it grows from a child to teen (in Rainbow-colored Bus) and finally to an adult (Flavor of Life)

Notice that there is a version of FOL already earlier on the album. This shows that the person earlier on who had died during Take 5 is the same as the only we are hearing about now. The person is only taking a different form

To put it graphically

<------------------------------------------------------->
FOL (ballad) Take 5 Boku wa Kuma RCB FOL
^----------------------------------------------------^
Same song but different versions, same theory applies to my idea of the HEART STATION perso's life.