Saving associated not working, only saving the main entity data with no erros

Glad you solved it.

The issue here comes from

 foreach ($recibo->pagamentos as $pagamento) {
     $pagamento->pagamento_situacao_id = 2;
 }

The reason is that due to the way that PHP handles object references, the original Recibo entity never gets told that the pagamentos property has been modified (Because the property has not been directly modified)