Sonic speed issue

Okay so a while ago I asked how to have the character speed up over time and someone really helped here by posting a video discussing the topic: Unreal Engine 4 Blueprints - Increasing Character movement speed while moving - YouTube

But there is an issue here. If I plug the function into two axis nodes (i.e. Forwards/Backwards and Left/Right) The function doesn’t work either way. Here some images to help.

Have you set the default values for the custom float variables?

MinimumMovementSpeed = 0
MaximumMovementSpeed = 4050
SprintMultiplyer = 4
DefaultMovementSpeed = 600