REST API: Operation is not valid due to the current state of the object

I am having issues accessing data from a DAC that has any amount of customization with it. I have a DAC with a few more complicated modifications, so I will start with the simple one. I have modified the External Reference field of SO.SOOrder. This is the only change to the DAC.

Originial Attributes

[PXDBString(40, IsUnicode = true)]
[PXUIField(DisplayName = "External Reference")]

Customize Attributes (Replace Original)

[PXDBString(40, IsUnicode = true)]
[PXUIField(DisplayName = "Some Text Here")]

Now, when I attempt to access any SalesOrder via the REST API:

GET https://site.acumatica.com/entity/Default/17.200.001/SalesOrder/SO000123

The following error is returned:

{
    "message": "An error has occurred.",
    "exceptionMessage": "Operation is not valid due to the current state of the object.",
    "exceptionType": "System.InvalidOperationException",
    "stackTrace": "   at PX.Api.ContractBased.EntityService.FillEntityImplWithKeys(String version, String name, EntityImpl entity, String[] keys)
   at PX.Api.ContractBased.SystemContracts.V2.SoapFacade.PX.Api.ContractBased.IRestGate.FillEntityImplWithKeys(EntityImpl entity, String[] keys)
   at PX.Api.ContractBased.SystemContracts.V2.RestController.CreateEntityFromKeys(String objectName, String idsString)
   at lambda_method(Closure , Object , Object[] )
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)
   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Web.Http.Filters.ActionFilterAttribute.<CallOnActionExecutedAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Filters.ActionFilterAttribute.<ExecuteActionFilterAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
}

Now, I'm not certain if this is occurring because of my DAC modification or not, but I cannot find anything else linking this and my other troubled DAC CustomerLocation to the same error message.

Where do I go from here to identify what what the bad state is?

Since this screen contains multiple key fields (Order Type and Order Nbr.), you need to put them all in the URL.

GET https://site.acumatica.com/entity/Default/17.200.001/SalesOrder/SO000123

gets changed into if this is a type SO Sales Order

GET https://site.acumatica.com/entity/Default/17.200.001/SalesOrder/SO/000123

SO is order type and 00123 is Order number