Custom fields only showing in Invoice edit screen

Hello I am using Manager version 26.3.26.3225 desktop version with Windows 11 Home on Dell Laptop 16 Plus 2-in-1. Model #DB06250.

I have added custom fields to sales invoices but they only show in the edit Invoice screen and not on the paid in full invoice. This is for internal use only and does not to be printed on invoices.
Let me tell you what I am wanting to do. We sell smoke alarms and customers sometimes ring up saying they have a fault. I show them how to reset the device which fixes the problem, However I want to be able to keep a record of the fault, in case it ever comes up again, which gives us extra quality control. Even better would be to create a flag (even a drop down box iwth a tick or cross) on our invoices to show where there has been an issue. I have checked to box “ do not show on printed invoice ”and do not copy or clone this information” Hope you can help as all the information shows it should be showing on the invoice screen, so I must not have completred the correct set up to get it ti function kind regards Mifs