If you hit something that looks like a bug, please check the known errors on the Saxon project pages at SourceForge. Also check the list archives.
If you need to submit attachments, this is best done through the Support Requests tracker on the SourceForge site.
Saxon-EE users are provided with an email address that allows bug reports to be sent to Saxonica privately if preferred.
The open source code of Saxon-B is maintained in a Subversion repository on the SourceForge site. This exists solely to provide early access to source patches, it is not (currently) used to deliver incremental releases of new functionality. Building the Jar files is reasonably easy for an experienced Java programmer; an Ant script is provided to assist with this, but it is likely to require customization to local requirements (for example, deleting the parts concerned only with Saxon-EE or Saxon on .NET). Building the .NET product is considerably more complicated, and although scripts are provided, it should only be attempted if you have a good knowledge of both platforms.