The blueprint code in OP is creating a whole new Level Sequence Player every time ‘R’ is pressed. This will result in many sequence players being active animating the same objects. When more than one track in sequencer animates the same property at the same time, the result will be a weighted average of all the tracks. This is true across all currently active level sequences and allows for seamless blending between sequences.
In this instance, please ensure that you are only calling Create Level Sequence Player a single time to be sure that there is only ever one sequence active. You could store the resulting player as a variable in your BP to call SetPlaybackPosition in future if you needed to.