1066 Not unique table/alias

[fantismic]

Hi, im having this error and for what i found it should be fixed, so im guessing im doing something wrong.
Here is my builder:

public function builder(): Builder
    {
        return Membership::query()
            ->join('conciliations as conciliation', function ($conciliation) {
                $conciliation->on('memberships.conciliation_id', '=', 'conciliation.id');
            })
            ->join('user_concs as user', function ($user) {
                $user->on('memberships.conciliation_id', '=', 'user.conciliation_id');
                $user->on('memberships.username', '=', 'user.username');
            })
            ->where("memberships.conciliation_id",'=','1')
            ->select(
                    'memberships.username as username', 
                    'memberships.profile as profile', 
                    'conciliation.application as application',
                    'user.fullname as fullname'
                );
    }

This is my columns function:

    public function columns(): array
    {
        return [
            Column::make("Aplicacion", "conciliation.application")
                ->sortable(),
            Column::make("Profile", "profile")
                ->sortable(),
            Column::make("Username", "username")
                ->sortable(),
            Column::make("Nombre", "user.fullname")
                ->sortable()
                ->searchable(),
        ];
    }

If i remove from the columns the joined fields it works fine, so im guessing im calling them wrong.
Can someone help me with this problem?
Thanks in advance!