Serialization and deserialization not supported. Path: $.TargetSite on Azure App Service

I have a Windows App Service with a Web API NET 7 deployed on that server. All of the endpoints are calling Cosmos db. There is no single error when tested and running locally via Visual Studio. The thing that makes me headache is these endpoints sometimes generate success result (http 200) but sometimes failed (http 500) and give this error message:

Most likely causes:
IIS received the request; however, an internal error occurred during the processing of the request. The root cause of this error depends on which module handles the request and what was happening in the worker process when this error occurred.
IIS was not able to access the web.config file for the Web site or application. This can occur if the NTFS permissions are set incorrectly.
IIS was not able to process configuration for the Web site or application.
The authenticated user does not have permission to use this DLL.
The request is mapped to a managed handler but the .NET Extensibility Feature is not installed.

Then I go to the Application Event Logs to see what happens and it shows this exception

Exception: 
System.NotSupportedException: Serialization and deserialization of 'System.Reflection.MethodBase' instances are not supported. Path: $.TargetSite.
 ---> System.NotSupportedException: Serialization and deserialization of 'System.Reflection.MethodBase' instances are not supported.
   at System.Text.Json.Serialization.Converters.UnsupportedTypeConverter`1.Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException(WriteStack& state, NotSupportedException ex)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCoreAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteCore[TValue](Utf8JsonWriter writer, TValue& value, JsonTypeInfo jsonTypeInfo, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Server.IIS.Core.IISHttpContextOfT`1.ProcessRequestAsync()

I don't have any JSON serialization containing this path $.TargetSite

Highly likely that the $.TargetSite refers to Exception's TargetSite property. Check your (custom) middlewares (for example exception handling or response logging ones) maybe they can perform some response serialization in case of exception. Also if you are throwing custom exceptions - try marking them with SerializableAttribute (helped me in some cases previously).