HTTP Cloud Function returns 500 but there is no errors in the logs

I'm getting a strange behaviour, I have a few http functions in Firebase Cloud Functions. They work perfectly, but there are days that they start returning status 500 for a while and then go back to working normal for a few minutes and then start returning status 500 again, this behaviour remains for the entire day.

The most strange part is that I don't get any error messages on my stack driver, in fact, there are no registries about these calls, it is as if the calls doesn't reach google's services somehow or it is just rejected and there are no registries about it.

I'll post the implementation of one of the most used functions in my application:

import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';

admin.initializeApp()

exports.changeOrderStatus_1 = functions.https.onRequest((request, response) =>
{
    //Check Headers
    const clientID = request.get('ClientID');

    if(clientID === null || clientID === undefined || clientID === "")
    {
        console.error(new Error('clientID not provided.'));
        return response.status(500).send('clientID not provided.');
    }

    const unitID = request.get('UnitID');

    if(unitID === null || unitID === undefined || unitID === "")
    {
        console.error(new Error('unitID not provided.'));
        return response.status(500).send('unitID not provided.');
    }

    //Check body
    const orderID = request.body.OrderID;

    if(orderID === null || orderID === undefined || orderID === "")
    {
        console.error(new Error('orderID not provided.'));
        return response.status(500).send('orderID not provided.');
    }

    const orderStatus = request.body.OrderStatus;

    if(orderStatus === null || orderStatus === undefined || orderStatus === "")
    {
        console.error(new Error('orderStatus not provided.'));
        return response.status(500).send('orderStatus not provided.');
    }

    const orderStatusInt = Number.parseInt(String(orderStatus));

    const notificationTokenString = String(request.body.NotificationToken);

    const customerID = request.body.CustomerID;

    const promises: any[] = [];

    const p1 = admin.database().ref('Clients/' + clientID + '/UnitData/'+ unitID +'/FreshData/Orders/' + orderID + '/Status').set(orderStatusInt);

    promises.push(p1);

    if(notificationTokenString !== null && notificationTokenString.length !== 0 && notificationTokenString !== 'undefined' && !(customerID === null || customerID === undefined || customerID === ""))
    {
        const p2 = admin.database().ref('Customers/' + customerID + '/OrderHistory/' + orderID + '/Status').set(orderStatusInt);

        promises.push(p2);

        if(orderStatusInt > 0 && orderStatusInt < 4)
        {
            const p3 = admin.database().ref('Customers/' + customerID + '/ActiveOrders/' + orderID).set(orderStatusInt);

            promises.push(p3);
        }
        else
        {
            const p4 = admin.database().ref('Customers/' + customerID + '/ActiveOrders/' + orderID).set(null);

            promises.push(p4);
        }

        let title = String(request.body.NotificationTitle);
        let message = String(request.body.NotificationMessage);

        if(title === null || title.length === 0)
            title = "?????";

        if(message === null || message.length === 0)
            message = "?????";

        const payload = 
        {
            notification:
            {
                title: title,
                body: message,
                icon: 'notification_icon',
                sound : 'default'
            }
        };

        const p5 = admin.messaging().sendToDevice(notificationTokenString, payload);

        promises.push(p5);
    }

    return Promise.all(promises).then(r => { return response.status(200).send('success') })
        .catch(error => 
            {
                console.error(new Error(error));
                return response.status(500).send(error)
            });
})

And this is how I invoke it, the client application is running on Xamarin Forms app usinde the c# language:

        static HttpClient Client;

        public static void Initialize()
        {
            Client = new HttpClient();
            Client.BaseAddress = new Uri("My cloud functions adress");
            Client.DefaultRequestHeaders.Add("UnitID", UnitService.GetUnitID());
            Client.DefaultRequestHeaders.Add("ClientID", AuthenticationService.GetFirebaseAuth().User.LocalId);
        }

  public static async Task<bool> CallChangeOrderStatus(OrderHolder holder, int status)
        {
            Debug.WriteLine("CallChangeOrderStatus: " + status);

            try
            {
                var content = new Dictionary<string, string>();

                content.Add("OrderID", holder.Order.ID);
                content.Add("OrderStatus", status.ToString());
                
                if (!string.IsNullOrEmpty(holder.Order.NotificationToken) && NotificationService.ShouldSend(status))
                {
                    content.Add("CustomerID", holder.Order.SenderID);
                    content.Add("NotificationToken", holder.Order.NotificationToken);
                    content.Add("NotificationTitle", NotificationService.GetTitle(status));
                    content.Add("NotificationMessage", NotificationService.GetMessage(status));
                }

                var result = await Client.PostAsync("changeOrderStatus_1", new FormUrlEncodedContent(content));

                return result.IsSuccessStatusCode;
            }
            catch (HttpRequestException exc)
            {
#if DEBUG
                ErrorHandlerService.ShowErrorMessage(exc);
#endif
                Crashes.TrackError(exc);

                return false;
            }
        }

These functions are called several times a minute at a time but can go for up to an hour without being called.

I have sent the requests from mobile conections, wifi conections, wired conections and from various internet providers and the problem still happens nonetheless.

Am I doing something wrong? Am I missing something? Is it instability in google servers?