Save or publish WF ends with error: Value does not fall within the expected range

Hello,

on our on premise SharePoint 2010 server with Nintex Workflow 2010 I am suddenly not able to save or publish (even empty) WF over my library.
When I try to save new WF I got error:
Server was unable to process request. ---> Value does not fall within the expected range.

In SharePoint log I can then see more detailed message:
(http://intranet/_vti_bin/NintexWorkflow/Workflow.asmx😞 Nintex.Workflow.NWException: Value does not fall within the expected range. ---> System.ArgumentException: Value does not fall within the expected range.
at Microsoft.SharePoint.SPFolderCollection.get_Item(String urlOfFolder)
at Nintex.Workflow.AutoStartRuleCollection.GetMetadataFolder(SPList list)
at Nintex.Workflow.AutoStartRuleCollection.LoadFromList(SPList list)
at Nintex.Workflow.Publishing.Publish.<>c__DisplayClass11.<HandleConditionalStartRules>b__e()
at Microsoft.SharePoint.SPSecurity.<>c__DisplayClass4.<RunWithElevatedPrivileges>b__2()
at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode)
at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(WaitCallback secureCode, Object param)
at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(CodeToRunElevated secureCode)
at Nintex.Workflow.Publishing.Publish.HandleConditionalStartRules(WorkflowType workflowType, Dictionary`2 parameters, Guid listId, SPContentTypeId contentTypeId, SPWeb web, String workflowName, XomlWorkflow xomlWorkflow, NWActionConfig workflowDataConfig, Boolean publishing)
at Nintex.Workflow.Publishing.Publish.SaveAWorkflow(String wfName, NWActionConfigurations configs, Guid listId, SPWeb web, ImportContext importCtx, SPContentTypeId contentTypeId, String changeNotes)
at NintexWorkflowWS.SaveWorkflow(String wfName, String activityConfigs, Guid listId, String contentTypeId, String changeNotes)
--- End of inner exception stack trace --- (Build:2230)

All other libraries and lists work ok.
On this specific library there is already another WF which was working so far, but during last editing I made a mistake and all new instances of WF failed (one step was to create item in another list, but with empty instead of valid number which cause error). I tried to correct it, but Im not able to save new version of WF as well (with the same error).

Do you have any tips what should I focus on?

Thanks #JK