In my company we are using Warehouse Management and we are using Next Empty Bin strategy for storage type.Please let me know how it behaves where no empty bins are there.
Even then system will throw error message TO can not be created. Mixed stock and addition to stock comes in to picture where system already proposed a empty bin( as in your case) and you want to use a bin which has a stock already. In that case, you can scan the existing bin.
I hope this will calrify doubts.