For some reason in our state environment I am getting the following exception from the default form submit controller. It doesn't appear to happen locally or in production but I have noticed this error and I'm wondering if this is a database issue. I can create a basic form with 2 fields and the form submits fine. If I go back to add another field, copy the form, or do anything the form breaks. 

I was once using custom form container block but we have since switched off of it due to an error (currently open thread related to that).

2016-07-20 14:25:54,633 [329] ERROR EPiServer.Global: 1.2.5 Unhandled exception in ASP.NET
Newtonsoft.Json.JsonSerializationException: Unexpected end when deserializing object. Path 'formGuid', line 1, position 50.
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ThrowUnexpectedEndException(JsonReader reader, JsonContract contract, Object currentObject, String message)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at EPiServer.Framework.Serialization.Json.JsonObjectSerializer.Deserialize[T](TextReader reader)
   at EPiServer.Forms.Implementation.ProgressiveSubmitInfoService.GetProgressiveSubmitInfo(Guid formContentGuid, HttpContextBase httpContext)
   at EPiServer.Forms.Implementation.DataSubmissionEngine.PerformDataSubmit(NameValueCollection rawSubmittedData, HttpContextBase httpContext, ControllerBase controller)
   at EPiServer.Forms.Controllers.DataSubmitController.Submit()
   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.ControllerActionInvoker.<>c__DisplayClass15.b__12()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at EPiServer.Forms.Controllers.FormsMvcHandler.ProcessController(IController controller)
   at EPiServer.Forms.Controllers.FormsMvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
Newtonsoft.Json.JsonSerializationException: Unexpected end when deserializing object. Path 'formGuid', line 1, position 50.
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ThrowUnexpectedEndException(JsonReader reader, JsonContract contract, Object currentObject, String message)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at EPiServer.Framework.Serialization.Json.JsonObjectSerializer.Deserialize[T](TextReader reader)
   at EPiServer.Forms.Implementation.ProgressiveSubmitInfoService.GetProgressiveSubmitInfo(Guid formContentGuid, HttpContextBase httpContext)
   at EPiServer.Forms.Implementation.DataSubmissionEngine.PerformDataSubmit(NameValueCollection rawSubmittedData, HttpContextBase httpContext, ControllerBase controller)
   at EPiServer.Forms.Controllers.DataSubmitController.Submit()
   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.ControllerActionInvoker.<>c__DisplayClass15.b__12()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at EPiServer.Forms.Controllers.FormsMvcHandler.ProcessController(IController controller)
   at EPiServer.Forms.Controllers.FormsMvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Anyone have any idea wha'ts going on here? 

EDIT:

This appears to only occur on 2nd submission and beyond. Does not occur on the first submission of a form

EDIT Again:

For some reason it behaves perfectly in my local environment. It only breaks when hosted in IIS (and multiple sites are having the issue). I reverted my form customizations, ran the remote DB that IIS is running from locally and do not have any issues. It's only when running in IIS for some reason.