This is not a bug per se because it does what you advertise, but the touch controls are inherently backwards. Swiping to the left makes the video go forward. The inherent sequence would be for swiping to the left to make the video go backwards similar to the left arrow on a keyboard. Likewise, swiping to the right makes the video go backwards. The inherent sequence would be for the video to go forwards when swiping to the right similar to the right arrow key.
If this is an easy fix then it should be a no brainer :). Swiping for then previous and next subtitles really needs to follow the direction of the arrow keys.