A testing function for seeing where a BP Docs delete is going wrong.

test-bp-docs-delete-cb.php

<?php 
// Remove the default
remove_action( 'bp_actions', 'bp_docs_process_folder_delete_cb' );
// Add the troubleshooting version
add_action( 'bp_actions', 'my_tshoot_bp_docs_process_folder_delete_cb' );

/**
 * Catch a request to delete a folder.
 *
 * @since 1.9.0
 */
function my_tshoot_bp_docs_process_folder_delete_cb() {
	if ( ! bp_docs_is_folder_manage_view() ) {
		bp_core_add_message( 'Not manage view.' );
		return;
	}

	$folder_id = 0;
	if ( isset( $_GET['delete-folder'] ) ) {
		$folder_id = intval( $_GET['delete-folder'] );
	}

	if ( ! $folder_id ) {
		bp_core_add_message( 'Folder ID not known.' );
		return;
	}

	$nonce = '';
	if ( isset( $_POST['_wpnonce'] ) ) {
		$nonce = stripslashes( $_POST['_wpnonce'] );
	}

	if ( ! wp_verify_nonce( $nonce, 'bp-docs-delete-folder-' . $folder_id ) ) {
		bp_core_add_message( 'Bad nonce.' );
		return;
	}

	if ( ! current_user_can( 'bp_docs_manage_folder', $folder_id ) ) {
		bp_core_add_message( 'User does not have permission.' );
		return;
	}

	if ( empty( $_POST['delete-confirm'] ) || '1' !== $_POST['delete-confirm'] ) {
		bp_core_add_message( 'Missing delete-confirm POST data.' );
		return;
	}

	$deleted = bp_docs_delete_folder( array(
		'folder_id'       => $folder_id,
		'delete_contents' => true,
	) );

	if ( $deleted ) {
		bp_core_add_message( __( 'Folder deleted.', 'bp-docs' ) );
	} else {
		bp_core_add_message( __( 'Could not delete folder.', 'bp-docs' ) );
	}

	bp_core_redirect( remove_query_arg( 'delete-folder', bp_get_requested_url() ) );
	die();
}