Negative inventory causing incorrect average costs - Millions

Hi,

We have had 3 x SKU's go into negative quantity on hand (MYOB never allowed this to happen previously).

Now we have a stock holding of millions of dollars for these items which are incorrect. We have looked at builds and purchase orders for these products and nothing has changed. However, it seems either a credit note has caused this or the stock going into a negative?

Not sure if it coincides.. we did a back up yesterday and now this error has appeared. Are we better off asking an accountant to fix or MYOB.

Any help would be greatly appreciated.

Thank you

Andy