We have identified that the issue is happening only with specific Visual Studio compiler versions, which is why it was not caught during our internal testing. We are currently working on a hotfix to address the issue.
In the meantime, we suggest that you make the necessary changes to the “InstaLODMeshReduction\Source\InstaLODUI\Private\Slate\InstaLODWindow.cpp” file on your local machine. You can fix it by updating line 515 from: