We are running through our processes in a test environment that we updated from Forms 10.4.4 to 10.4.5. One of the processes is throwing an error when trying to submit the form at the second approval step. After the first approval step, Forms kicks off a couple of workflows that write variables values back to the instance. At the second approval step, the user changes 1 field (radio button) and clicks the submit button. At this time, they are presented with a LFF502-Unexpcted Error message. In the Forms Admin log it records the following error:

An unexpected error has occurred. [LFF502-UnexpectedError]

Details:
URL: /Forms/Form/Submit?source=formiframe
Error: UnexpectedError
Date: 10/28/2022 1:50:27 PM (US Mountain Standard Time)
HTTP Status Code: 500
Business Process ID: 6
User: fmuser
IP: 169.254.13.154
Browser: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Safari/537.36
Business Process Name: AP - Invoice Approval Forms

Stack Trace:
Caught exception: Laserfiche.Forms.CommonUtils.Exceptions.LFFormsException
Message: An unexpected error has occurred. [LFF502-UnexpectedError]


Inner exception: System.FormatException
Message: Input string was not in a correct format.
   at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at E_Forms.Models.ViewModels.Form.Submit.getAttrIdToRowCountMapping(IEnumerable`1 fieldsToProcess, Dictionary`2 last_submission)
   at E_Forms.Models.ViewModels.Form.Submit.ValidateForm(HttpRequestBase request, cf_forms form, Dictionary`2 Lookupdata, FormDataSet formdata, Dictionary`2 FieldsToIgnore, NameValueCollection formFields, Dictionary`2 ItemsInSection)
   at E_Forms.Models.ViewModels.Form.Submit.RetrieveDataFromForm(HttpRequestBase request, FormDataSet formdata, List`1& NoChangedElements, Boolean SaveAll)
   at E_Forms.Controllers.FormController.Submit(FormCollection collection)
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_0.<InvokeActionMethodFilterAsynchronouslyRecursive>b__0()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_6.<BeginInvokeAction>b__4()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult)

I see that the message says, "Input string not in a correct format', but is there any way to narrow down which field is the problem?