APP-AR-11621: You cannot enter a negative Receipt Amount for Cash Receipt.

Would anyone know why they system will SOMETIMES disallow negative "Net Receipt Amount"  to be entered even when you select the 'Receipt Type' of 'Misc'. When I select receipt type of misc it defaults back to standard and the error message appears. Also the issue occurs sporadically, sometimes it allows you enter negative net receipt amount and process.

Thanks for your input.