One of the challenges with ASP classic is that the ASP classic processor is not a true compiler. The only code that is ever formally checked by the ASP processor is the code that is actually executed by real world page requests. You can have functions that are completely invalid and if they are not called, you would never know about it. When we are translating a site, all the code on all the pages and their includes is compiled. It is not uncommon for problems in the code to show up. The tool does its best to interpret what it sees, but if there are problems in the source they often produce problems with the .NET.
Sometimes there are things we can do with the translator to accept bad or unconventional code, other time we have to use the pre-editor, and in the worst cases we have to hand fix files.
It is also very common for an ASP site to contain files that were never finished, or have not been maintained and are no longer consistent with the rest of the site also have problems generating a clean correct translation and they should be brought to the attention of the customer to ask if they are still an active part of the site. In active pages should be omitted from the translation project. IN this way, the upgrade project is a good opportunity to clean up the site by removing the inactive content.