Bundles cannot contain multiple application packages for the same Windows 10 processor architecture

Question

I am updating (porting) an existing application from 8.1 to Windows 10. When I try to create a package, I get this error:

The package with the file name "MyWindows10App_1.1.0.0_x64.appx" and the full name of the package "26637BetsySoft.Myversion81App_1.1.0.0_x86__grkkn6rpr1pew" in the bundle is not valid, because the bundle also contains the package with the file name "MyWindows10App_1.1.0x_86. the name of the package is “26637BetsySoft.Myversion81App_1.1.0.0_x86__grkkn6rpr1pew” which refers to the same processor architecture.
 Bundles cannot contain multiple application packages for the same processor architecture or architecture-oriented package with any architecture-specific application package.

My Windows 8.1 application was downloaded as appxBundle, and for this reason VS claims that a package will be created by default. Does anyone have any suggestions? I tried to change the "platform target" and the configuration for the build (several different configurations). I can’t get past the mistake.

additional messages:

• Package creation failed. C: \ WS_VS2015 \ WalkScore_W10 \ WalkScore_W10 \ MakeAppx
• Error 0x80080204 - The specified package format is not valid: the package manifest is not valid.