PackageCompiler.jl ERROR: ArgumentError: Package MyPackage not found in current path, maybe you meant `import/using .MyPackage`

Hi there,
I am really lost, trying to let PackageCompiler.jl create a sysimage within a docker, but somehow all packages don’t get added normally, but I need to access them from local modules with a prefixed dot using .MyPackage.

Does anyone has any idea what could go on?

EDIT: the same script which creates the sysimage is running successfully on a nixos, and I can import using MyPackage the standard way, however executing the sysimage generator within docker I need to run using .MyPackage.
EDIT: I am using a local registry, maybe it is just that…