MBS is configured to write verbose log data for each module build to /var/tmp (the BUILD_LOGS_DIR setting), and this log file is included in the cg import for the module build. However, these log files are all empty.
This appears to be a regression in version 3.
The files are created, but all zero length.
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/koji/mbs/issues/1702
Please continue any further discussion there.