Unable to archive with arm64

[fuggly]

Hiyas

I have a main project "X" with two iOS Universal Frameworks "RMTXKit" and "RMUIKit" (which uses RMTXKit). Now, I set this all up to use all standard architectures, set "Build only valid architectures" to "NO" and I can compile and build the project fine. it works perfectly and the lib is fun to use.
However.. if I archive the whole thing, it doesn't work anymore. The build process ends with this here:

** BUILD SUCCEEDED **

Create universal static library
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/libtool -static /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/AdHoc Testflight/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/AdHoc Testflight/BuildProductsPath/AdHoc Testflight-iphonesimulator/RMTXKit.framework/Versions/A/RMTXKit -o /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/AdHoc Testflight/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit.temp
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/libtool: for architecture arm64 object: /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/AdHoc Testflight/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit(DBCredentials.o) malformed object (unknown load command 1)
Showing first 200 notices only
Command /bin/sh failed with exit code 1

I have no idea what this is or where this comes from. Its only when archiving, that this happens, when I normal build, it works. Does anyone know what I can do here?

Thanks

[fuggly]

And... if I try to just archive the very first framework that is used, RMTXKit, then I get this:

** BUILD SUCCEEDED **

Create universal static library
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/libtool -static /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/RMTXKit/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/RMTXKit/BuildProductsPath/AdHoc Testflight-iphonesimulator/RMTXKit.framework/Versions/A/RMTXKit -o /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/RMTXKit/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit.temp
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/libtool: for architecture arm64 object: /Users/misteli/Library/Developer/Xcode/DerivedData/Gugus/Intermediates/ArchiveIntermediates/RMTXKit/BuildProductsPath/AdHoc Testflight-iphoneos/RMTXKit.framework/Versions/A/RMTXKit(DBCredentials.o) malformed object (unknown load command 1)
Showing first 200 notices only
Command /bin/sh failed with exit code 1

Just building the framwork works fine, but archiving fails. Does anyone know what this is?