DIAGNOSIS Expected behavior of the Mini-LED local dimming zones. Blooming around small, bright objects on dark backgrounds is a physical limitation.
FIX Go to Settings > Picture > Advanced Settings > Local Dimming. Change from 'High' to 'Medium' or 'Low'. This reduces the halo effect at the cost of peak black level.
IF THAT DIDN'T WORK For subtitles specifically, change the subtitle color to a light gray instead of pure white in the app's settings (like Netflix or Disney+).
HEADS UP This is not a defect. The 'High' setting maximizes contrast but makes blooming more visible. There is no setting that eliminates it completely.