Customary I don't have my
subtitles somewhere in the middle or at the top of my movie, but somewhere at the bottom.
So I used "Custom position" to move them to those custom positions.
(I tested mid-movie and at top of the window).
The most recent manually chosen position is remembered. (Also for another movie not played before)!
Isn't that what custom position means? ... or don't you just want to read what I write?
P.S. Using
big sized characters does not help! I simply don't have and/or can reproduce your problem.