Currently this are my findings

1. NULL PAYMENT CARD LIMIT

this is caused by createPaymentCard in PaymentCardSynchronizationManager.swift because

private func createPaymentCard(_ psPaymentCard: PSPaymentCard?) -> PaymentCard? {
        guard let psPaymentCard = psPaymentCard else {
            return nil
        }

        let paymentCard = PaymentCard()
        paymentCard.id = psPaymentCard.id
        paymentCard.cardOwnerId = psPaymentCard.cardOwnerId
        paymentCard.accountOwnerId = psPaymentCard.accountOwnerId ?? psPaymentCard.cardOwnerId
        paymentCard.expirationDate = psPaymentCard.expirationDate
        paymentCard.deliveryDate = psPaymentCard.shippingDate ?? Date().addingTimeInterval(604800)
        paymentCard.accountNumber = psPaymentCard.accountNumber
        paymentCard.maskedNumber = psPaymentCard.maskedNumber
        paymentCard.ownerName = psPaymentCard.nameOnCard
        paymentCard.visualType = psPaymentCard.visualType

        if let main = psPaymentCard.main {
            paymentCard.main = main
        }

        if let accountOwnerId = psPaymentCard.accountOwnerId {
            paymentCard.accountOwnerId = accountOwnerId
        }

        paymentCard.status = psPaymentCard.status
        paymentCard.type = psPaymentCard.account?.type

        // we are creating here a new instance of Payment card limit if the paymentCard.limit == nil, but the problem is it will always // be nil because it is always a new instance thus the "let paymentCard = PaymentCard()""
        if paymentCard.limit == nil {
            paymentCard.limit = PaymentCardLimit()
        }
        return paymentCard
    }

2. DUPLICATE CARD LIMIT

since in number 1 we created a new row in realm for Payment Card limit that has no value (NULL) in

private func synchronizeCardLimit(for paymentCards: [PaymentCard]) -> [Promise<Bool>] {

        return paymentCards.map { paymentCard -> Promise<Bool> in
            Promise<Bool> { value in
                self.paymentCardApiManager
                    .getPaymentCardLimit(accountNumber: paymentCard.accountNumber)
                    .done { psPaymentCardLimit in

                            // here we are creating again a new instance of payment card limit but now
                            // we are putting some value from psPaymentCardLimit
                            // so everytime "synchronizeCardLimit" is called we are adding new value in realm
                            let paymentCardLimit = self.createPaymentCardLimit(psPaymentCardLimit)
                        try! self.realm.write {
                            // this doest not actually update the old value of "paymentCardLimit" but insert a new one
                            // but updates the paymentCard.limit with new Object
                            paymentCard.limit = paymentCardLimit
                            value.fulfill(true)
                        }
                    }.catch { error  in
                        value.reject(error)
                }
            }
        }
    }


    Possible solution so far

    private func createPaymentCard(_ psPaymentCard: PSPaymentCard?) -> PaymentCard? {
        guard let psPaymentCard = psPaymentCard else {
            return nil
        }

        let paymentCard = PaymentCard()
        paymentCard.id = psPaymentCard.id
        paymentCard.cardOwnerId = psPaymentCard.cardOwnerId
        paymentCard.accountOwnerId = psPaymentCard.accountOwnerId ?? psPaymentCard.cardOwnerId
        paymentCard.expirationDate = psPaymentCard.expirationDate
        paymentCard.deliveryDate = psPaymentCard.shippingDate ?? Date().addingTimeInterval(604800)
        paymentCard.accountNumber = psPaymentCard.accountNumber
        paymentCard.maskedNumber = psPaymentCard.maskedNumber
        paymentCard.ownerName = psPaymentCard.nameOnCard
        paymentCard.visualType = psPaymentCard.visualType

        if let main = psPaymentCard.main {
            paymentCard.main = main
        }

        if let accountOwnerId = psPaymentCard.accountOwnerId {
            paymentCard.accountOwnerId = accountOwnerId
        }

        paymentCard.status = psPaymentCard.status
        paymentCard.type = psPaymentCard.account?.type

//        let paymentCard = self.paymentCardRepository
//        .findAll()
//        .filter { paymentCard in
//            return paymentCard.id == psPaymentCard.id
//        }.first

        // ##################### BUT IS CRASHES HERE #################
        if let paymentCard = self.paymentCardRepository.find(psPaymentCard.id),
            let paymentCardLimit = paymentCard.limit
        {

            paymentCard.limit = paymentCardLimit

        } else {
            paymentCard.limit = PaymentCardLimit()
        }
//
//        if paymentCard.limit == nil {
//            paymentCard.limit = PaymentCardLimit()
//        }

        return paymentCard
    }


private func synchronizeCardLimit(for paymentCards: [PaymentCard]) -> [Promise<Bool>] {

        return paymentCards.map { paymentCard -> Promise<Bool> in
            Promise<Bool> { value in
                self.paymentCardApiManager
                    .getPaymentCardLimit(accountNumber: paymentCard.accountNumber)
                    .done { psPaymentCardLimit in
//                        let paymentCardLimit = self.createPaymentCardLimit(psPaymentCardLimit)
                        try! self.realm.write {
                            paymentCard.limit.amount = psPaymentCardLimit.amount.amount
                            paymentCard.limit.currency = psPaymentCardLimit.amount.currency
                            value.fulfill(true)
                        }
                    }.catch { error  in
                        value.reject(error)
                }
            }
        }
    }