To prevent the bug from ever happening again:
The water-freeze mechanic requires precise timing. At 144 FPS, the freeze effect expires 2.4x faster than intended, causing the Prince to fall through before the climbing animation finishes. Capping to 60 FPS restores the original intended logic.
Several contributing factors have been identified:
Search for the " Prince of Persia Forgotten Sands Observatory Fix " on trusted modding sites like PCGamingWiki.
If the script is permanently broken and your save file is corrupted, the fastest way to continue playing without restarting the entire game is to download a clean community save file that starts exactly after the Observatory doors.