Gradle sub-modules could not be found

Question

I've the following gradle project structure:

SUPER/
|______A/
|       |______A1/
|       |       |______build.gradle
|       |______A2/
|       |       |______build.gradle
|       |______build.gradle
|       |______settings.gradle
|
|______B/
|       |______build.gradle
|       |______settings.gradle
|
|______build.gradle
|______settings.gradle

My build.gradle from the A-Project contains somethings like that:

...
project(":A1") {
    apply plugin: "java-library"


    dependencies {
        api project(":A2")
    }
}

project(":A2") {
    apply plugin: "java-library"


    dependencies {
        ...
    }
}
...

My "Super"-settings.gradle file contains something like that:

rootProject.name = 'SUPER'

include 'A'
include 'B'

In my sub-project "A" the settings.gradle looks like that:

include 'A1', 'A2'

When calling the gradlewrapper like that "./gradlew SUPER:A1:sometask" on the command line from the SUPER-folder, it fails with the message:

FAILURE: Build failed with an exception.

* Where:
Build file 'C:\Users\<somepath>\SUPER\A\build.gradle' line: 44

* What went wrong:
A problem occurred evaluating project ':A'.
> Project with path ':A1' could not be found in project ':A'.

But when doing something like that "./gradlew A1:sometask" from the A-sub-project-folder, it works successfully.

can you explain me what am I'm doing here wrong?