RMS Inventory Issues

One of our clients is having issues with inventory. They will
frequently have items with wrong quantities in their system. Theft is
most likely not the issue since some of the items missing are large,
conspicuous items like mags of wine or 30 packs of beer. Every single
time, the amount of sales and the amount incoming will add up, but
they will still be short in the store. They are running RMS with SP3.