Performing a hot reload on a project that is using a local binary build of the Engine will sometimes result in the Engine's UE4Editor.version file being updated with a new BuildId value. That results in the Editor being unable to open the project after it is closed since the BuildId value no longer matches the values for when the various modules were built when the local binary build was created.
Yes. This behavior was not observed in 4.17.
This requires a local binary build of the Engine to be available. One can be built with the following command (will take some time to complete): RunUAT.bat BuildGraph -target="Make Installed Build Win64" -compile -script=Engine/Build/InstalledEngineBuild.xml -set:HostPlatformOnly=true -set:WithDDC=true
The Editor fails to open successfully, and displays a message that numerous Engine modules are missing or built with a different engine version.
The Editor continues to open successfully after each hot reload.
In some cases, closing the Editor and doing a normal, non-hot reload, build in Visual Studio allows the Editor to open normally again until another few hot reloads are performed.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-55072 in the post.