Cannot use typescript class from other local typescript module using browserify

I have a common npm module containing TypeScript which is an node module providing some classes and functionality. This module is packaged via browserify + tsify and also exports the declaration files and built with gulp.

I have another npm module using TypeScript which imports this module locally via file:../modulename and tries to use functionality from the first module. The second module is also packaged via browserify + tsify and built with gulp. The compilation of the second module works via npx tsc, but fails if I execute the gulp build file with the error message

Error: Cannot find module './AbstractClass' from 'folderInOtherModuleContainingTheJSFiles'

Interestingly it sometimes fails with this Class sometimes with another, so it seems there is also some kind of concurrent processing.

I extracted the failing code from my project and created a minimal example with this behavior here.

npm version: 5.6.0 node version: v9.5.0