Hi I'm new to Umbraco and would appreciate help with the following scenario - my content tree is structured as below:

• Home Page

  • Projects

    • Project 1
    • Project 2

This is my Controller:

public class ProjectsController : UmbracoApiController
    {
        private readonly UmbracoHelper _umbracoHelper;

        public ProjectsController(UmbracoHelper umbracoHelper)
        {

            _umbracoHelper = umbracoHelper;
        }

        [HttpGet]
        public List<IPublishedContent> FilterProjects(string? product, string? style, string? space, string? architect, string? installer)
        {
            // get 'projects' node
            var node = _umbracoHelper.Content(Guid.Parse("017b9615-4809-4f96-9c8c-212ecb5ce18d"));
            if (node is null) return null;

            List<IPublishedContent> returnedChildren = new List<IPublishedContent>();

            foreach (IPublishedContent _child in node.Children)
            {
                bool matched = false;

                var products = _child.GetProperty("products").GetValue() as IEnumerable<IPublishedContent>;
                if (products != null && products.Any())
                {
                    foreach (var _product in products)
                    {
                        if (product != null && product.Split(',').Contains(_product.Name.Trim()))
                        {
                            matched = true;
                        }

                        if(style != null && style.Split(',').Contains(_product.Parent.Name.Trim()))
                        {
                            matched = true;
                        }

                    }
                }

                var spaces = _child.GetProperty("space").GetValue() as IEnumerable<string>;
                if(spaces != null && spaces.Any())
                {
                    foreach(string _space in spaces)
                    {
                        if (space != null && space.Split(',').Contains(_space.Trim()))
                        {
                            matched = true;
                        }
                    }
                }

                var architects = _child.GetProperty("architect").GetValue() as IEnumerable<string>;
                if (architects != null && architects.Any())
                {
                    foreach (string _architect in architects)
                    {
                        if (architect != null && architect.Split(',').Contains(_architect.Trim()))
                        { 
                            matched = true;
                        }
                    }
                }

                var installers = _child.GetProperty("installer").GetValue() as IEnumerable<string>;
                if (installers != null && installers.Any())
                {
                    foreach (string _installer in installers)
                    {
                        if (installer != null && installer.Split(',').Contains(_installer.Trim()))
                        {
                            matched = true;
                        }
                    }
                }

                if (matched)
                {
                    returnedChildren.Add(_child);
                }
            }


            return returnedChildren;
        }
    }

I'm comparing strings because most of the properties in my Document Type are of Tags type (with the exception of products which is of Treepicker type)

This however throws an exception stating JsonException: A possible object cycle was detected. This can either be due to a cycle or if the object depth is larger than the maximum allowed depth of 32. Consider using ReferenceHandler.Preserve on JsonSerializerOptions to support cycles.

It seems to me that the whole Content Tree is being returned instead of just the filtered Project nodes.

Any help would be very much appreciated.