Issues to access Swift code located in ObjC static library

I have an iOS app with the following configuration:

• My own ObjC static library project - MyStaticLib
• My own ObjC app target project - MyApp
• I have both projects in the same Xcode workspace so that MyStaticLib is linked successfully to MyApp
• Both projects have a mix of ObjC and Swift code successfully working.

Currently:

• MyStaticLib: ObjC code can access Swift code and vice versa
• MyApp: ObjC code can access Swift code and vice versa
• ObjC code from MyApp can access ObjC code from MyStaticLib (This is achieved by adding Copy Files in Build Phases at MyStaticLib project settings with the ObjC header files)

Objective:

• Swift code located in MyApp to access Swift code located in MyStaticLib

Issues:

• If I'm trying to call a public Swift function located in MyStaticLib from MyApp, I get Cannot find 'YYY' in scope.
• If I'm adding import MyStaticLib, I get dozens of Duplicate interface definition for class 'ZZZ'

Any idea how to resolve this?