I can’t replicate your issue, on 14.2. But I have seen this type of thing in the past (ETC blowing Finish Date out to 2039), typically when allocating new team members to in-flight project where there exists a ‘fast plan’ task with ID = ~rmw and actual hours booked to task. Today, can’t replicate this, no matter what I try (perhaps I’m still missing something, too).
One thing you might check under Admin\Project Management\Settings is the Requisition Booking field. Ours is set to “Use Allocation Percentage.”
Wish I could say when this field came into being. I’ve changed the value to “Use Available Work Units” with no effect – perhaps it needs to have the app restarted to take effect. IFF some of your resources have no available work units, and some do, THEN this setting might have something to do with your scenario.
I can’t test this further, as this is not what I’m getting paid for. I do have interest in the root cause/solution as this might be a future issue for us, as we are finally starting down WBS/Scheduling path.