When I'm troubleshooting I always use Display Text in a window actions wherever appropriate, so I get persistent info/error messages that are easily edited.
When something cancels a macro it's frequently a good idea to consult the Keyboard Maestro Engine log.
~/Library/Logs/Keyboard Maestro/Engine.log
See my macro here:
Open the Keyboard Maestro Engine Log in the Console or BBEdit
** BBEdit is commercial software, but it reverts to a freeware "lite" version after a demo period. Even the lite version is very powerful – it has PCRE RegEx search and replace, is highly AppleScriptable, and has many other useful features. Commercial vs Freeware Comparison Chart.