Level 70 crafting and gathering tasks auto-cancel when the delivery box is full
If you have crafting and/or gathering tasks in progress, and they are of mixed levels, then when the delivery box gets full and all tasks are in a completed state awaiting pick-up, one of the level 70 tasks will completely cancel rather than automatically restarting. Each time the delivery box gets full like this where all tasks are completed and the result is awaiting pick-up, then one level 70 task will cancel instead of restarting.
You've got these Jewelcrafting tasks running: Raw Gold Ingot, Slate Whetstone, Gold Needle. You also have these Gathering tasks running: Gold Sand, Slate, and Crate of Astral Diamonds. The "Gold Needle" task and the "Crate of Astral Diamonds" task are both level 70. The rest of the tasks are level 68 or 69 (varies). You don't empty the delivery box for 24 hours. When you finally do, all the tasks are completed and the results are awaiting pick-up. When you empty the delivery box, all the level 68 and 69 tasks will automatically restart. However, either "Gold Needle" or "Crate of Astral Diamonds" will not; instead, it will be canceled and you'll have to order the artisan to perform the task again.
Let's assume that "Crate of Astral Diamonds" is the task that canceled and did not restart. Let's also assume you just can't be bothered to go to the Workshop to restart that task. Now, you ignore the delivery box for another day, which causes it to be completely full with all tasks completed and the results awaiting pick-up. When you collect the deliveries, once again all of the level 68 and 69 tasks will have restarted. However, "Gold Needle" being a level 70 task will be canceled. So you'll have only these tasks in progress: Raw Gold Ingot, Slate Whetstone, Gold Sand, and Slate. Even if you let the delivery box get completely full again, all of these tasks will automatically restart.
How to Reproduce
Start two level 70 tasks that take the same amount of time to complete. Use artisans that have matching speed modifiers so that these tasks will complete at the same time. Order the artisans to perform the task as many times as possible.
In the last 10 minutes before those tasks will complete, start a low level task (below level 15 is best) that you can repeatedly complete using morale. Order the artisan to perform the task as many times as possible. Tasks that require only 5 morale to instantly complete are the best choices.
NOTE: It is critical that you start the task as normal because completing it using morale will put all the results into the delivery box. If you do not start the task first, then all the results will go directly to your inventory.
Once started, use morale to complete the low level task until the delivery box is full. Wait for the two level 70 tasks to complete. Once they are complete and the delivery boxes slots are full with results awaiting pick-up, empty the delivery box. Notice that your low level task has restarted as has one of the level 70 tasks, while the other level 70 task has not restarted.
I expect that all tasks will automatically restart once the delivery box has been emptied, and that none of the tasks will cancel.