CSV SO Import error, enter amount?

I am intermittently receiving an error that states 'Please enter value for amount'. It happens randomly, and I cannot determine what I am doing wrong.

I am trying to import new sales orders into the system. I am mapping the following fields:

Warehouse Location, Customer, Memo, Customer Message, Status, PO#, Shipping Cost, Date, Order #, Item, and Quantity

On an individual basis, these files upload flawlessly. I run into the issue most often when trying to upload multiple orders at once. Sometimes I have the problem, sometimes I don't. It asks me to 'Enter a value for amount'. I normally copy and paste the data from the results file, and re-submit... this will normally work. I'm confident that the original files are clean and have no hidden values or formatting.