Tasks can not be moved across lanes, with the error "STATE(resolved, new, etc states) is not a valid state for incident", after adding Task Type (sys_class_name) to a task's form layout with lane field set to "state".
1) Add Task Type (sys_class_name) field to any task type via Form Layout, i.e. incident, to the VTB view if existing, or else to the Default view.
2) Add a task of the same task type to a freeform board, as follows:
Name: something say "lanes by state for incident"
Owner: system administrator
Task table: incident
Lane field: state
Filter: "task type" is "incident".
3) Open the VTB board.
4) Move tasks across lanes, i.e. from 'New' to 'In progress'. The error "In Progress is not a valid state for Incident" shows up.
After carefully considering the severity and frequency of the issue, and the cost and risk of attempting a fix, it has been decided to not address this issue in any current or near future releases. We do not make this decision lightly, and we apologise for any inconvenience.
As a workaround, remove the Task Type (sys_class_name) field via Form Layout for VTB or Default views.