Since I updated ADT from 16 to 18 (which mandated Proguard update from 4.6 to 4.8), Proguard has been acting very weirdly (and inconsistently?).

The latest such problem is when I try to export a signed (release) APK, I receive the following errors:

Proguard returned with error code 1. See console
Warning: com.bta.LibProj2: can't find referenced class com.bta.R$string
Warning: com.bta.MyDlg1: can't find referenced class com.bta.R$string
Warning: com.bta.MyMenu: can't find referenced class com.bta.R$menu
Warning: com.bta.R: can't find referenced class com.bta.R$attr
Warning: com.bta.R: can't find referenced class com.bta.R$drawable
Warning: com.bta.R: can't find referenced class com.bta.R$menu
Warning: com.bta.R: can't find referenced class com.bta.R$string
Warning: com.bta.myapp.MyAppActivity$1: can't find referenced class com.bta.myapp.MyAppActivity
Warning: com.bta.myapp.MyAppActivity$ELicenseResponse: can't find referenced class com.bta.myapp.MyAppActivity
Warning: com.bta.myapp.MyAppActivity$MyLicenseCheckerCallback$1: can't find referenced class com.bta.myapp.MyAppActivity$MyLicenseCheckerCallback
Warning: com.bta.myapp.MyAppActivity$MyLicenseCheckerCallback$1: can't find referenced class com.bta.myapp.MyAppActivity
Warning: com.bta.myapp.R$array: can't find referenced class com.bta.myapp.R
Warning: com.bta.myapp.R$layout: can't find referenced class com.bta.myapp.R
Warning: com.bta.myapp.R$xml: can't find referenced class com.bta.myapp.R
Warning: there were 49 unresolved references to classes or interfaces.
         You may need to specify additional library jars (using '-libraryjars').
java.io.IOException: Please correct the above warnings first.
    at proguard.Initializer.execute(Initializer.java:321)
    at proguard.ProGuard.initialize(ProGuard.java:212)
    at proguard.ProGuard.execute(ProGuard.java:87)
    at proguard.ProGuard.main(ProGuard.java:493)

I did notice the recommendation to add -libraryjars

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