We have a problem with flexi tasks in Nintex (126.96.36.199 latest version). It seems related to the december SP2019 CU. When a user wants to handle a task (which was already started before the CU, so with a running workflow). An error occurs. This is the ULS:
Failed to retrieve form from workflow. Error: Value cannot be null. Parameter name: s. Stack trace: at System.IO.StringReader..ctor(String s) at Nintex.Workflow.WorkflowConfig2010.LoadWorkflowConfig(String configXml) at Nintex.Workflow.Forms.ControlTemplates.TaskForm.GetWorkflowConfig() at Nintex.Workflow.Forms.ControlTemplates.TaskForm.GetForm(String formKey, FormData formData, Boolean hasEnterpriseLicense) b8b68da0-cd82-0049-f307-c0152e223f98
Anybody an idea what the cause can be and how to resolve this? Thanks.