This issue appears to be a continuation of
UE-42205. Hot reloads work successfully in projects that were created in 4.15 or 4.16 and are still using the same Engine version that they were created in. However, if a project was created in 4.15 and then upgraded to 4.16, the same failure as mentioned in the previous ticket occurs.
This repro requires both 4.15 and 4.16 to be installed.
The build fails in Visual Studio, stating that it failed to produce a .lib file for the project. The error message will appear similar to: ERROR : UBT error : Failed to produce item: D:\Unreal Projects\Current Issues\TestHotReload1 4.16\Intermediate\Build\Win64\UE4Editor\Development\UE4Editor-TestHotReload1-7685.lib
The build completes successfully.
Head over to the existing AnswerHub thread and let us know what's up.