SUMMARY
adding the "Freeze" effect to freeze a frame in combination with adding a subtitle causes the video to become greyish - loss of contrast, for the duration of the freeze frame.


STEPS TO REPRODUCE
1.  Select a short clip and apply the "Freeze" effect. Works as it should.
2.  Add a subtitle track, the project monitor window looses contrast.
     Performing the subtitle before adding the "freeze" effect also has the same issue.
     The loss of contrast also appears in the rendered output.
3.  I even tried adding the "freeze" effect without the subtitle, then adding the edited sequence to a new sequence with just the subtitle, but the problem still exists.

OBSERVED RESULT
When the "freeze" effect is used in combination with a subtitle track the video for the duration of the freeze has lower contrast. 


EXPECTED RESULT
Adding a subtitle track should not change the contrast of output.

SOFTWARE/OS VERSIONS
Linux: Ubuntu 24.04 LTS
Windows:  not tried
macOS: not tried
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma:    Kdenlive 24.08.03 appimage
KDE Plasma Version: ???
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0
MLT  7.28.0

ADDITIONAL INFORMATION
Workaround found.
use (right click - Extract frame to project) from Project Monitor window and then add the extracted frame as a clip instead of using the "freeze" effect. Add subtitle as required - no loss of contrast.