the information on the post doesn't seem sufficient to troubleshoot the issue. could you advise what are the steps you take to create those sales return orders
If the issue could be replicated, it will help for deep dive.
As per the screenshot attached by you, it can be seen that the Qty on Sales Return Line = 1, however, in the Item Tracking you've selected two rows defining 1-1 qty with the same lot no., I hope making correction in the Item Tracking Lines would resolve your issue.
Errors like this are usually down to issues with the item tracking. Can you confirm if these orders relate to items that need to be lot tracked? If so then I would check the items and confirm that the quantity on the line does not match the quantity defined on the item tracking.
If you can send screen shots then that would be helpful.