Character unnecessary step down during PHYS_Flying mode

When MovementMode is set to PHYS_Flying, the character may unexpectedly step down by MaxStepHeight when colliding with a wall near a ceiling.

This occurs because UCharacterMovementComponent::StepUp() performs a step-down movement assuming a successful upward step, even when the upward sweep is blocked by a ceiling. As a result, the character is moved downward by up to MaxStepHeight despite no actual step-up having occurred.

Note:

UCharacterMovementComponent::StepUp() internally performs the following sequence:

1. Sweep upward by MaxStepHeight
2. Sweep forward
3. Sweep downward by MaxStepHeight

When the upward sweep (step 1) is blocked by a ceiling, the actual upward movement is less than MaxStepHeight (or zero). However, the step-down phase (step 3) does not take this into account and still applies the full step-down distance.

This logic is valid for walking movement but causes unintended behavior when StepUp() is executed during PHYS_Flying in some geometry conditions.

1. Download the repro project from the attachment.
2. Run the project and start PIE.
3. Press F to switch the character into Flying mode.
4. Press Space to move the character upward and let it touch the ceiling.
5. Move the character toward a nearby wall.
6. Observe that the character steps downward when colliding with the wall.

Expected Result

• While in PHYS_Flying mode, colliding with walls or ceilings should not cause any step-up or step-down behavior.
• The character should remain at the same vertical position when horizontal movement is blocked.

Actual Result

• When the character hits a wall near a ceiling during PHYS_Flying, the character is moved downward by approximately MaxStepHeight.