With multiple projects open in a session, where they are using cmake presets, then when asked to "Reload CMake Presets" the other project(s) appear to get into a broken parsing state.
This then sometimes prevents the current project from being able to parse the presets.

Activating the project that is in the broken state appears to trigger the preset processing, which then succeeds.

The behaviour is tricky to reproduce and somewhat intermittent.  However, it seems to be that the presets (json) file needs to be open in the IDE.

A video reproduction has been captured.