If you create a debit or invoice in the AR transactions screen and use a "#" in the document/check description, the document number will not be found when trying to apply a payment to it. The reason behind this is that MetalTrax and GlassTrax are written in the Visual Basic programming language. In this programming language, the "#" symbol is used to give a command in programming. Therefore, anything following a "#" in the tables would be perceived by the program as a command.
Contact KSS and have a tech support agent access your tables to edit the document/check description and remove the "#" or other symbol causing the issue.