TYPO3 Core

This bug took me ages to figure out, because no error is thrown!
If you have 2 or more site-roots (for 2 or more different websites in one T3 instance), the backend form-module lists only forms defined in the first root-page. All definitions in the 2nd or following site-roots are ignored.

Example setup:

MyT3Instance
- FirstSiteRoot (UID 1)
  - SubPage1
  - SubPage2
  - ...
- SecondSiteRoot (UID 9)
  - SubPage1
  - SubPage2
  - ...

Inside the template of FirstSiteRoot I include the bootstrap_package, which comes with a custom form-setup.

module.tx_form.settings.yamlConfigurations.110 = EXT:bootstrap_package/Configuration/Form/Setup.yaml

Inside the template of SecondSiteRoot I include the bootstrap_package, AND have also a custom form-setup in user_mysecondsiteextension.

module.tx_form.settings.yamlConfigurations.300 = EXT:user_mysecondsiteextension/Configuration/Form/MyCustomSetup.yaml

If you select the form-module now, you'll see ONLY the "Contact Form" defined by bootstrap_package (EXT:bootstrap_package/Resources/Private/Forms/Contact.form.yaml),
because it seems the form-module recognizes ONLY form setups from the first occurring page-root in the sitetree.
If you now move up the SecondSiteRoot BEFORE the FirstSiteRoot, the form-module lists both forms (the bootstrap_package one and EXT:user_mysecondsiteextension/Resources/Private/Form/mycustom.form.yaml)

Expected behaviour:
The form-module should look into ALL root-pages and list all forms which it finds.