Amount Changes when adding an item

I have tried to find some info in the forum without much success.

When adding some items from  the inventory and you add the item on a direct invoice, it changes the quantity from 1 to three and changes the price from 1850 to 666.67 which is then equal to 1850.01.

I have checked the item code and there is no characters in the code.

When I go back and edit the line item the quantity can be changed but the amount now remains at 666.67 and needs to manually changed back to the selling price of 1850. When I then add, the amount and the price is correct. There is also no characters in the description field.

Any idea what could cause this?

Regards

Wynand