EPiServer ServiceApi installation breaks all of our internal API's

Question

We are on CMS 11 and Commerce 13. I just got the ServiceApi (5.6.1) and ServiceApi.Commerce (5.6.1) installed on our site and with some configuration enabled the site to start without errors. The site wouldn't start until I added the following line to my web.config:

<add key="episerver:serviceapi:maphttpattributeroutes" value="false" />

However, after these steps, our internal system APIs are broken when they worked before. There is a WebApiConfig.cs file that is what sets up our internal APIs but I'm not sure what would fix this. When sending a query off that connects to our API and populates a datatable, these are the errors we get:

GET http://localhost:65238/api/library/list?sEcho=2&iColumns=4&sColumn…ow&bRegex=false&iSortCol_0=0&sSortDir_0=asc&iSortingCols=1&_=1719429175236 500 (Internal Server Error)
Uncaught Error: DataTables warning: table id=DT_MSDSList - Ajax error. For more information about this error, please see http://datatables.net/tn/7
    at Ot (master.min.js:27:2081)
    at Object.error (master.min.js:26:14625)
    at u (master.min.js:3:7199)
    at Object.fireWith [as rejectWith] (master.min.js:3:7948)
    at n (master.min.js:4:11376)
    at XMLHttpRequest.<anonymous> (master.min.js:4:16221)

Another error thrown during trying the QuickOrder, which is API on the site

quickorder.ts:52 

GET http://localhost:65238/api/quickorder/getProductNameAutocomplete?term=d&size=5 500 (Internal Server Error)

WebApiConfig.cs file that is the only place I see anything API related in the entire solution. Opti support said something about there being no XMLMediaTypeFormatter, which was being removed in the WebApiConfig.cs for reasons I'm unaware of by a past partner. Commenting out that line was the last step to get the site to start without an exception.

using System;
using System.Net.Http.Formatting;
using System.Net.Http.Headers;
using System.Web.Http;
using EPiServer.Framework;
using EPiServer.Framework.Initialization;
using Newtonsoft.Json;

namespace CMS.Ellsworth.Business.Initialization
{
[InitializableModule]
[ModuleDependency(typeof(FrameworkInitialization))]
    public class WebApiConfig : IInitializableModule
    {
        public static string ApiRoute = "api";

        public void Initialize(InitializationEngine context)
        {
            // Enable Web API routing
            GlobalConfiguration.Configure(config =>
            {
                config.MapHttpAttributeRoutes();

                var formatters = GlobalConfiguration.Configuration.Formatters;
                var jsonFormatter = formatters.JsonFormatter;
                var settings = jsonFormatter.SerializerSettings;

                var enumConverter = new Newtonsoft.Json.Converters.StringEnumConverter();
                jsonFormatter.SerializerSettings.Converters.Add(enumConverter);
                config.Formatters.Add(new BrowserJsonFormatter());

                settings.Formatting = Formatting.Indented;

                // Commented out due to it throws System.NullReferenceException: Object reference not set to an instance of an object.
                // If its uncommented, it will throw an exception when the site is started.
                // config.Formatters.Remove(config.Formatters.XmlFormatter);

                config.Routes.MapHttpRoute(
                    name: "DefaultEpiApi",
                    routeTemplate: ApiRoute + "/{controller}/{id}",
                    defaults: new { id = RouteParameter.Optional });
            });
        }

        public void Uninitialize(InitializationEngine context)
        {
        }
    }

    public class BrowserJsonFormatter : JsonMediaTypeFormatter
    {
        public BrowserJsonFormatter()
        {
            SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
            SerializerSettings.Formatting = Formatting.Indented;
        }

        public override void SetDefaultContentHeaders(Type type, HttpContentHeaders headers, MediaTypeHeaderValue mediaType)
        {
            base.SetDefaultContentHeaders(type, headers, mediaType);
            headers.ContentType = new MediaTypeHeaderValue("application/json");
        }
    }
}

Has anyone encountered this or know what to do to get my API's to work again?