If you use the SetInputModeUIOnly blueprint node while an axis event is held down (eg you’re moving) then it continues to use the value the axis event had when the input mode was changed, even when you let go of the key (to continue the example, you keep moving in the direction you were holding down). I would expect the axis value to instead go back to 0 until you switch the input mode back.
I repro’d this in a blank project by creating a new BP project from the 3rd person template, adding the following input event to the character
then starting PIE and pressing ‘i’ while moving. I tested and found this present in 4.11 and 4.13 preview 1 as well.