If you’re getting these very rare but still mysterious errors:

Started executing script ‘Deploy-FabricApplication.ps1’. Test-ServiceFabricApplicationPackage : The BuildLayout of the application in
c:\Temp\TestApplicationPackage_3811564851592\icw0q1rk.bus\Release is invalid. Code is missing for service MyWebApiPkg.

or

Register-ServiceFabricApplicationType : The BuildLayout of the application in
C:\SfDevCluster\Data\ImageBuilderProxy\AppType\a9f07f16-1fda-4319-a5e6-829f38a8f093 is invalid. Code is missing for service MyWebApiPkg.

when trying to debug a Service Fabric application locally or just packaging it then make sure Build Configuration Manager settings match:

Any discrepancy in Platform or Build would cause the said errors.