I'm afraid the subs-problem might be "burned" into the video, so that it cannot be rectified.
In full screen try if the cut-off parts of the subs are hidden by the screen edges or if you can make them show completely by panning out:
1. Depress (together): [Shift]/[O] (i.e. the letter O not the digit 0=zero).
2. Move the slider to the left
Results?
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P.S.:
Perhaps "Cut top and bottom of video in full screen mode" is selected under
(rightclick >) Options > Preferences > Video [General] ?