Since live composer 1.5.53, it overwrites the post_content field with rendered live composer code. This should happen. Please revert to logic from version 1.5.52. I've done a demo video here:
https://youtu.be/GxxdQ-UEIXs
I believe this is part of the offending code, where it sets post_content to the rendered page builder code:
This was bug that got removed here in 28th Feb 2025:
2d4e2c6
Before being added back, even though it shouldn't have been on 30th June 2025:
45551c8