If you need to debug code that deals with printing in 4D it is advisable to first hide the printing dialogs before attempting to debug such code. This is because the printing dialogs are Modal windows and will prevent you from being able to continue debugging the code causing you to get stuck.

The solution is to hide the printing dialogs first, before attempting to debug the code.

It can be hidden via code:

SET PRINT OPTION(Hide printing progress option;1) // hide printing progress

The visibility can also be toggled from the Interface page of the Database Settings.