Error message with no clue about the issue

Hi,
We use SDL Knowledge Center 12.
 
A topic got accidentally added to the bookmap <backmatter> element rather into the publication's Resources. As a result, the output failed with the error message:

W:\InfoShare\App\Utilities\DITA-OT\dita-ot-2.5.4_zoomin\plugins\org.dita.base\build_preprocess.xml:55: Failed to run pipeline: Illegal character in scheme name at index 0: 68040:%20H0X_AppendixNum:%20Appendix%20B:%20Log%20Messages

It took really long to identify the issue. The error message does not help in any way identifying the cause for the issue.
 
User friendly error messages would definitely help here.
 
Thanks,
Kavitha