Steps to Reproduce
Add a Task Type (sys_class_name) field to any task via Form Layout.
Add a task of the same task type to a freeform board.
Note that links to records on a card or in card details will be formatted incorrectly, for example, [object%20Object].do?sys_id=XXXXXXXXXXXX&sysparm_view=&sysparm_view_forced=true&sysparm_time=1479149003426
Remove the Task Type (sys_class_name) field from the task's form layout.
Related Problem: PRB724038