Why are you adding undefined steps to workflow templates? there should not be any, they are only created to be replaced by a real step when, for example, you add a fork.
when do you receive the error message? - when activating the workflow template? (in which case kindly add a printscreen) or is workflow runtime instance in a development system in which case you can simply start a new one.
P.S
By the numbers of your nodes (11938, 3461) I assume it is a huge workflow in which case you should consider using sub-worklfows or it's a heavily modified one, in which case you should try to see what is the reason for all the changes.