Failed to Update Custom Fields by using Custom Action

I have created a few fields in BAccountExt as shown below and placed them under a custom tab in Customers screen:

1. UsrValue1 - string
2. UsrValue2 - string
3. UsrValidValue - boolean (field disabled to disallow manual update)
4. UsrValue1ValidatedDateTime

The flow of this customization is when validateValue action button is pressed, it will trigger validation on UsrValue1 and UsrValue2 via API and return the status (true/false). The status will then be saved to UsrValidValue field, and the validation date time will be recorded in UsrValue1ValidatedDateTime field. 

The action button code is as shown below: 

protected void validateValue()
{
    bool flag = true;
    Customer customer = (Customer)Base.CurrentCustomer.Current;

    if (customer != null)
    {
        // Retrieve customer's BAccount from the current context
        BAccount customerAccount = Helper.GetCustomer(customer.BAccountID);
        BAccountExt customerAccountExt = customerAccount.GetExtension<BAccountExt>();

        // Retrieve company's BAccount from the current context
        BAccount companyAccount = Helper.GetCompanyAccountFromContext();

        if (companyAccount == null)
        {
            // Acuminator disable once PX1050 HardcodedStringInLocalizationMethod [Justification]
            throw new PXException("Company account not found.");
        }

        string apiBaseUrl = companyAccount.GetExtension<BAccountExt>().UsrApiBaseUrl;
        string idValue = companyAccount.GetExtension<BAccountExt>().UsrIDValue;

        if (string.IsNullOrEmpty(apiBaseUrl) || string.IsNullOrEmpty(idValue))
        {
            // Acuminator disable once PX1050 HardcodedStringInLocalizationMethod [Justification]
            throw new PXException("API base URL or ID value is null or empty.");
        }

        // Retrieve access token
        string accessToken = null;
        try
        {
            var accessTokenTask = TokenManager.GetAccessTokenAsync(companyAccount, flag); // Override token manager for Customers screen
            accessToken = accessTokenTask.GetAwaiter().GetResult();
        }
        catch (Exception ex)
        {
            PXTrace.WriteError(ex);
            // Acuminator disable once PX1050 HardcodedStringInLocalizationMethod [Justification]
            throw new PXException("Failed to retrieve access token.");
        }
        finally
        {
            string value1 = customer.GetExtension<BAccountExt>().UsrValue1;
            string value2 = customer.GetExtension<BAccountExt>().UsrValue2;
            try
            {
                var apiCallSuccessTask = ValidateValueHelper.ValidateValue(apiBaseUrl, value1, value2, accessToken);
                var apiCallSuccess = apiCallSuccessTask.GetAwaiter().GetResult();

                customerAccountExt.UsrValidValue = apiCallSuccess; // Update checkbox if success
                PXTrace.WriteInformation($"Value validation result: {apiCallSuccess}");
            }
            catch (Exception ex)
            {
                PXCache<BAccount>.GetExtension<BAccountExt>(customerAccount).UsrValidValue = false; // Update checkbox if failed
                // Acuminator disable once PX1050 HardcodedStringInLocalizationMethod [Justification]
                throw new PXException("Value is invalid. Please review and validate again.");
            }
            finally
            {
                customerAccountExt.UsrValue1ValidatedDateTime = DateTime.Now; // Always update the validation date/time

                // Update the cache
                this.Base.Caches[typeof(BAccount)].Update(customerAccount);
                this.Base.CurrentCustomer.Update(customer);

                // Save changes to the database
                this.Base.Actions.PressSave();
                PXTrace.WriteInformation($"Record saved.");
            }

        }
    }
}

I confirmed from trace that the code passes through all checkpoints:

API Response Status Code: OK

Value is valid 

Value validation result: True

Record saved.

Despite all that, the values remained unchanged in Customers screen. Please advise on this.