One user gets error when clicking "Send" for shoppingcart. An error has occurred

Hi.

We've just upgraded to 9.2.1 with reinstall of Web portal and Appserver.
Everything seems to work fine, but ONE user on our admin team struggles with sending PWOs for other users.

The user has the same rights as the rest of us in the team. When shoppingcart has been checked out and the user press "send", an error appears: "An error has occurred".
In the web portal log we're getting the following error:

2024-08-22 09:08:25.8709 ERROR ( WebLog qn114moq0drmxlhm0x4vsgqt) : VI.Base.ViException: An exception has occurred while running the form method F0_ctl00_ControlRef8_ControlRef15_ControlRef15_ControlRef8b_Main_Main_Container6_Container7_Button4_Method. VI.Base.ViException: An exception has occurred while running the form method F0_ctl00_ControlRef8_ControlRef15_ControlRef15_ControlRef8b_Main_Main_Container6_Container7_Button4_Method. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at VI.WebRuntime.LocalColumn.SetValueAsync(IDataRow row, Object newValue, CancellationToken ct)
at VI.WebRuntime.VI_StandardWeb.VI_ITShop_CartCalculateCheckStatus.<GetAction>d__1e.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 VI.WebRuntime.VI_StandardWeb.VI_ITShop_ShoppingCart_Form.<ServerActionCall2_Action>d__e2.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 VI.WebRuntime.CallActionFormMethod.<>c__DisplayClass30_0.<<ExecuteAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at VI.WebRuntime.ActionQueue.<RunActionQueueInternalAsync>d__7.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 VI.WebRuntime.CallActionFormMethod.<ExecuteAsync>d__30.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 VI.Base.SyncActions.Do(Func`1 action)
at VI.WebRuntime.Compatibility.SyncExtensions.Execute(IFormMethod formMethod, HttpContextBase context, IFormRenderPart renderPart, CancellationToken ct)
at VI.WebRuntime.FormMethodHandler.ExecuteFormMethod(HttpContextBase context, String renderPartId, IDictionary`2 parameters, String clientId)
--- End of inner exception stack trace ---
at VI.WebRuntime.FormMethodHandler.ExecuteFormMethod(HttpContextBase context, String renderPartId, IDictionary`2 parameters, String clientId) at VI.WebRuntime.FormMethodHandler.ExecuteFormMethod(HttpContextBase context, String renderPartId, IDictionary`2 parameters, String clientId)

I know the error is very generic, but maybe you experts have some tips. 
We've tried resetting user profile locally, deleting cookies and everything that follows. 

The user also tried the same operation in Chrome, Firefox, IE and Edge.