Well, you seem to have a handle on most things leveling so I give you credit. A couple of questions: 1. Did you try clearing leveling and see if the assignment delay was maintained? That’s my first guess but I assume from our conversation that the answer is no. 2. Could the task have had an actual start date? That would have locked the task start but still move remaining work as best as it could. I’m guessing the answer is still no, but it sounds like a potential result of turning off its ability to split tasks.
I’ve run across situations where it’s difficult to assess. If you’re like me and doesn’t like to give u without an answer, I might suggest recreating that task and see if it has the same behavior. I’m grasping a bit, but I’ve used leveling enough to know that it works well within its rules (but I have found recreating tasks to be an answer in some cases).
Again, good luck. Glad you found something that works.