relationshipmanager for belongsToMany relationship with pivot table tries to insert into wrong table

class UsersRelationManager extends RelationManager
{
    protected static string $relationship = 'users';

    protected static ?string $modelLabel = 'Student';

    protected static ?string $title = 'Enroll Students';

    protected static ?string $recordTitleAttribute = 'id';

    public static function form(Form $form): Form
    {
        return $form
            ->schema([
                Select::make('user_id')
                    ->label('Student')
                    ->required()
                    ->options(function (RelationManager $livewire): array {
                        // code to get the users
                    })
                    ->searchable(),
            ]);
    }