One user out of several thousand can't submit shoppingcart

Hi experts.

As the subject states, ONE out of several thousand users can't submit shoppingcart.
User has access to the web portal (we're using the old one). The user can add products to the shoppingcart, and is able to add several products. The user can use the "save" button, but when submitting the shoppingcart using "send" an error pops up. Every other user in our organization are able to do this except this one spesific user.

Errormessage:  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.

Tracelog states the following before the error:
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Releasing lock on connection 2
2024-12-20 15:15:57.9311 DEBUG ( ObjectLog hakgycnv1uwintr1sfufjbgj) : Flushing level 0
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync - read write, _transaction == 2217627
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Lock aquired on connection 2
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Use the transaction
2024-12-20 15:15:57.9311 DEBUG ( SqlLog hakgycnv1uwintr1sfufjbgj) : Setting DB context data to: user = Domain\User1, id = 426f288d-0310-4308-99e5-b1ce7188ba75, level = 0
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Releasing lock on connection 2
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync - read write, _transaction == 2217627
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Lock aquired on connection 2
2024-12-20 15:15:57.9311 TRACE ( SqlLog hakgycnv1uwintr1sfufjbgj) : ClaimConnectionAsync: Use the transaction
2024-12-20 15:15:57.9311 DEBUG ( SqlLog hakgycnv1uwintr1sfufjbgj) : (2 ms) - update ShoppingCartItem set CheckResult = 1, CheckResultDetail = N'{"UidShoppingCartItem":"48a6d2ef-2fbf-4d08-80a7-d05b604206bc","UidPersonWantsOrg":null,"Results":[{"$type":"QER.CompositionApi.ITShop.QerCartItemCheckResult, QER.CompositionApi","Submitted":false,"MissingMandatory":[],"IsForeignOrg":false,"IsForeignFunctionalArea":false,"HasInvalidParameters":false,"IsExistingAssignment":false,"DuplicateWith":[],"IsDuplicate":false,"IsTimeConflict":false,"Exclusions":[],"ExistingPwo":null,"HasExistingPwo":false,"HasWarnings":false,"HasErrors":false,"CanCommitSilently":false,"UidQerTermsOfUse":"b3e2e4a9-3bc5-4520-ba60-900302bd58c6","AcceptedTermsOfUse":false}],"Checks":[{"$type":"QER.CompositionApi.ITShop.Check.ForeignOrgCheck, QER.CompositionApi","Id":"ForeignOrgCheck","Status":4,"Title":"Check whether the recipient belongs to the same organizational unit as the requested product","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.ForeignFuncCheck, QER.CompositionApi","Id":"FuncForeign","Status":4,"Title":"Check whether the recipient belongs to the same functional area as the requested product","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.ExistingAssignmentCheck, QER.CompositionApi","Id":"ExistingAssignmentCheck","Status":1,"Title":"Check for existing assignments","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.DuplicateCheck, QER.CompositionApi","Id":"DuplicateCheck","Status":1,"Title":"Duplicate request check","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.RequestableCheck, QER.CompositionApi","Id":"RequestableCheck","Status":1,"Title":"Request permission check","ResultText":null,"Detail":{"IsTimeConflict":false,"IsMissingReason":false,"ExistingPwo":null,"Exception":null,"Warning":null}},{"$type":"QER.CompositionApi.ITShop.Check.ExclusionCheck, QER.CompositionApi","Id":"ExclusionCheck","Status":1,"Title":"Service item exclusion check","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.ProductDependencyCheck, QER.CompositionApi","Id":"ProductDependencyCheck","Status":1,"Title":"Mandatory service item check","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.TermsOfUseCheck, QER.CompositionApi","Id":"TermsOfUseCheck","Status":1,"Title":"Check whether the terms of use have been accepted","ResultText":null,"Detail":null},{"$type":"QER.CompositionApi.ITShop.Check.MandatoryParameterCheck, QER.CompositionApi","Id":"MandatoryParameterCheck","Status":1,"Title":"Check whether all mandatory information have been specified","ResultText":null,"Detail":null},{"$type":"CPL.CompositionApi.ITShop.CartItemComplianceCheck, CPL.CompositionApi","Id":"CartItemComplianceCheck","Status":0,"Title":"Check whether the request causes rule violations","ResultText":null,"Detail":null}],"HasWarnings":false,"HasErrors":false,"CanCommitSilently":false}', xdateupdated = GetUTCDate(), xuserupdated = N'Domain\User1' where (ShoppingCartItem.UID_ShoppingCartItem = '48a6d2ef-2fbf-4d08-80a7-d05b604206bc') and (ShoppingCartItem.CheckResult = 0) and (isnull(convert(nvarchar(max), ShoppingCartItem.CheckResultDetail), N'') = N'')