Why doesn't Ben need additional power to change himself again into the Thing in the 2005 Fantastic Four movie?

Question

In the 2005 Fantastic Four movie, when Reed invents a machine to cure the Fantastic Four, he is unsuccessful because the machine needs more power. Viktor uses the machine to cure Ben, by supplying the additional power from his own superpower.

A little later, Reed is captured by Viktor, and Sue and Johnny try to rescue him. In the meantime, Ben wonders what he could do to help them, his eyes lay on the machine, and he enters it to change himself back into the Thing.

But this time, the power is enough to change him. He does not need Viktor's additional power for the change.

Is it because the additional power is needed only to "cure" and not to change back, or is there some other reason I could not understand?

Answer 1

The chamber is capable of accurately replicating the storm, but to revert the individual to their original form requires additional power to "control the storm".

"Reed, stop," Sue begged him, not knowing where to hold him or what to do. "You need to rest your—" "The power ... I need . . . more power ... to control ... the storm . .

_{^{Fantastic 4 - Official Novelisation}}

Since the chamber is capable of recreating the storm, it's a simple matter of getting into it and turning it on if you want to make yourself fantastic again.