The Error check available from the Tools menu is a great way to run an initial check for errors, but it is non-specific to publish type. The final check is specific to the type of publish (offline, SCORM, or web-based, for example), which might help to explain why you’ll receive a number of additional errors and warnings at that time. We can definitely look into beefing up the Error Check in Tools, though, so that it’s more thorough and useful.
The Cancel button causing Lectora to freeze sounds like a bug, and I’ll be sure to write that up.
Thank you, Laura, that is a very reasonable answer. Indeed, many checks cannot be completed unless I specify what I publish for, so just clicking the Error Check doesn’t uncover everything. Here’s a suggestion. Maybe it’d be possible to do a two-step error checking, like “Check for general issues” and “Advanced Check” (where you’d have to specify SCORM/AICC/HTML as a target). A bit like “Quick scan” and “Deep scan” in antivirus software.