It sounds like you may be having hard drive failures.  I should would start making some backups of data. 

It sounds like you're potentially using Sage Drive for storing your data, or one of your computers acts as the host of the data (or server) and the other reads from that computer. Since both machines are missing groups of invoices, it is highly possible that you're looking at 2 different copies of the same company. If you are on-plan and need assistance determining if this is the case, please contact us at 866-747-3888.