Need to recompile Engine fron Rocket Build when opening a project

Hello everyone,

We are currently working with a custom Rocket build create from a Fork of the 4.18 branch of Unreal engine Sources.
We have no issues creating the Rocketbuild and distribute it to the team. But we have an issue when using it.

If we have a project opened with this version and we start the compilation of another project, UE4 ask to recompile every modules (cf screenshot) …
Once the issue popup, even closing the first project, we could not start another project without recompiling the engine or erase the RocketBuild installation with the last version.

Why does a project compilation modify the Rocket Build Folder ?
Is that because all Engine DLLs are used, that the Engine considering these as modified ?
We have no issue when opening a project alone and when it is the only one opened.

Both projects are in differents folders but using the same Engine
Rocket Build is created with this line

and the script InstalledEngineBuild used ( basically very similar to the sample one ) attached InstalledEngineBuild.txt (64.5 KB)

Thanks for any ideas.