All morphs for the Millennium Figures are designed to work well at a value of 1. Many of them even work well at values past one, or at negative values.
However, when multiple morphs that affect the same area of the model are used simultaneously, some of these morphs will often not work well at values of one. If you're encountering a problem applying a morph at values between zero and one, check to see what other morphs are applied that might be interfering.
For example, the "OpenMouth" and "Yell" morphs for the Millennium Figures both work well individually, but should not both be applied together at values of one. Another example would be how the full-body morph "Young" for Victoria 2.0 affects the head as well, and cannot be used at a value of one while the head morph "HeadYoung" is also set at one.