These errors appeared in our log files yesterday

2018-10-31 10:05:56,111 [10] ERROR Umbraco.Forms.Data.LogHelper [(null)] - [T10/D5] Forms: workflow 'Send email to [email protected] when submitted' failed on Submitted


System.IO.IOException: The process cannot access the file 'D:\xxxxxxxxxxxxxxxxxxxxxxxxxx\app_data\umbraco.licensing.log.txt' because it is being used by another process.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.StreamWriter.CreateFile(String path, Boolean append, Boolean checkHost)
   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize, Boolean checkHost)
   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding)
   at System.IO.File.InternalAppendAllText(String path, String contents, Encoding encoding)
   at Umbraco.Licensing.Validator.getLicenseFiles(String directory, String productName)
   at Umbraco.Licensing.Validator.GetAllLicenseFiles(String directory)
   at Umbraco.Licensing.Validator.Check()
   at Umbraco.Licensing.Validator.IsTrial()
   at Umbraco.Forms.Core.Licensing.IsTrial()
   at Umbraco.Forms.Core.Configuration.get_IsTrial()
   at Umbraco.Forms.Core.RecordField.ToXml(XmlDocument xd)
   at Umbraco.Forms.Core.Record.ToXml(XmlDocument xd)
   at Umbraco.Forms.Core.Providers.WorkflowTypes.SendEmail.Execute(Record record, RecordEventArgs e)
   at Umbraco.Forms.Core.Services.WorkflowService.ExecuteWorkflows(List`1 workflows, RecordEventArgs e)

and

2018-10-31 10:04:43,346 [29] ERROR Umbraco.Core.UmbracoApplicationBase [(null)] - [T29/D5] An unhandled exception occurred


System.IO.IOException: The process cannot access the file 'D:\xxxxxxxxxxxxxxxxxxxxxxxxxxxx\app_data\umbraco.licensing.log.txt' because it is being used by another process.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.StreamWriter.CreateFile(String path, Boolean append, Boolean checkHost)
   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize, Boolean checkHost)
   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding)
   at System.IO.File.InternalAppendAllText(String path, String contents, Encoding encoding)
   at Umbraco.Licensing.Validator.getLicenseFiles(String directory, String productName)
   at Umbraco.Licensing.Validator.GetAllLicenseFiles(String directory)
   at Umbraco.Licensing.Validator.Check()
   at Umbraco.Licensing.Validator.IsTrial()
   at Umbraco.Forms.Core.Licensing.IsTrial()
   at Umbraco.Forms.Core.Configuration.get_IsTrial()
   at Umbraco.Forms.Data.Storage.RecordFieldValueStorage.InsertRecordFieldValues(RecordField rf)
   at Umbraco.Forms.Data.Storage.RecordFieldStorage.InsertRecordField(RecordField recordfield)
   at Umbraco.Forms.Data.Storage.RecordStorage.InsertRecord(Record record, Form form)
   at Umbraco.Forms.Web.Services.RecordService.storeRecord(Record record, Form form) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Services\RecordService.cs:line 29
   at Umbraco.Forms.Web.Services.RecordService.Approve(Record record, Form form) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Services\RecordService.cs:line 107
   at Umbraco.Forms.Web.Services.RecordService.Submit(Record record, Form form) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Services\RecordService.cs:line 93
   at Umbraco.Forms.Web.Controllers.UmbracoFormsController.SubmitForm(Form form, FormViewModel model, Dictionary`2 state, ControllerContext context) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Controllers\UmbracoFormsController.cs:line 239
   at Umbraco.Forms.Web.Controllers.UmbracoFormsController.GoForward(Form form, FormViewModel model, Dictionary`2 state) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Controllers\UmbracoFormsController.cs:line 183
   at Umbraco.Forms.Web.Controllers.UmbracoFormsController.HandleForm(FormViewModel model, Boolean captchaIsValid) in f:\TeamCity\buildAgent\work\acce5a5136f4db35\Umbraco.Forms.Mvc\Controllers\UmbracoFormsController.cs:line 132
   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__DisplayClass42.<BeginInvokeSynchronousActionMethod>b__41()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass37.<>c__DisplayClass39.<BeginInvokeActionMethodWithFilters>b__33()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass4f.<InvokeActionMethodFilterAsynchronously>b__49()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<>c__DisplayClass2a.<BeginInvokeAction>b__20()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<BeginInvokeAction>b__22(IAsyncResult asyncResult)
   at System.Web.Mvc.Controller.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar)
   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Haven't been able to find what's causing them, but it's concerning that it looks like form submission is no longer working..

Anyone have any ideas?