python BeeWare briefcase: cannot package and adhoc-sign mac os app

Question

I am trying to package a python app for mac os. I am using the BeeWare briefcase package and I am following the offical tutotial

The package offers adhoc-signing which is needed to create the DMG for installation.

Here is the terminal output:

(beeware-venv) tk@MacBook-Pro-von-Tobias circledrawer % briefcase package --adhoc-sign 

[circledrawer] Signing app with ad-hoc identity...
Because you are signing with the ad-hoc identity, this app will run, but cannot be re-distributed.
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100.0% • 00:03

[circledrawer] Building DMG...
     ━━━━━━━━━━━━━━━━━━━━ Building Cricle Drawer-0.0.1.dmg...hdiutil: couldn't unmount "disk4" - Ressource ist belegt
     ━━━━━━━━━━━━━━━━━━━━ Building Cricle Drawer-0.0.1.dmg...hdiutil: couldn't unmount "disk4" - Ressource ist belegt
     ━━━━━━━━━━━━━━━━━━━━ Building Cricle Drawer-0.0.1.dmg...hdiutil: couldn't unmount "disk4" - Ressource ist belegt
     ━━━━━━━━━━━━━━━━━━━━ Building Cricle Drawer-0.0.1.dmg...hdiutil: couldn't unmount "disk4" - Ressource ist belegt
     ━━━━━━━━━━━━━━━━━━━━ Building Cricle Drawer-0.0.1.dmg...hdiutil: couldn't unmount "disk4" - Ressource ist belegt
Building Cricle Drawer-0.0.1.dmg...

Log saved to /Users/tk/Desktop/beeware-tutorial/circledrawer/logs/briefcase.2024_03_13-13_19_04.package.log

Traceback (most recent call last):
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/bin/briefcase", line 8, in <module>
    sys.exit(main())
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/lib/python3.10/site-packages/briefcase/__main__.py", line 29, in main
    command(**options)
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/lib/python3.10/site-packages/briefcase/commands/package.py", line 151, in __call__
    state = self._package_app(
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/lib/python3.10/site-packages/briefcase/commands/package.py", line 99, in _package_app
    state = self.package_app(app, **full_options(state, options))
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/lib/python3.10/site-packages/briefcase/platforms/macOS/__init__.py", line 845, in package_app
    self.dmgbuild.build_dmg(
  File "/Users/tk/Desktop/beeware-tutorial/beeware-venv/lib/python3.10/site-packages/dmgbuild/core.py", line 832, in build_dmg
    raise DMGError(callback, "Unable to detach device cleanly")
dmgbuild.core.DMGError: Unable to detach device cleanly

How can I fix this issue?