Function insert_field_widget_single_element_form_alter() in insert_media sub-module implements hook_field_widget_single_element_form_alter().
As the module name is insert_media, the correct name of the function should be
insert_media_field_widget_single_element_form_alter()
A function of the same name is also in the insert module, and it causes problems. For example, using phpstan will result in a fatal error.
PHP Fatal error: Cannot redeclare insert_field_widget_single_element_form_alter() (previously declared in /var/www/web/modules/contrib/insert/insert.module:742) in /var/www/web/modules/contrib/insert/modules/insert_media/insert_media.module on line 203
Rename insert_field_widget_single_element_form_alter web/modules/contrib/insert/modules/insert_media/insert_media.module
to insert_media_field_widget_single_element_form_alter.
Closed: duplicate
3.0
Code
Thanks for filing the issue. This should already be fixed in 3.0.0-beta2 → per issue #3381683 🐛 Duplicate function error insert media module Fixed . Please reopen if the problem still exists in 3.0.0-beta2.