There's a few things you need to know about the Tactical Office when it comes to custom missions. These things are here, but you are very much encouraged to go read through the Tactical Office website too, as it holds a lot more information. You can find the site here: http://tac.emperorshammer.org.
The Tactical Officer (or TAC), is the person in the Emperor's Hammer who is ultimately responsible for the release of new missions to the Mission Compendium. The TAC evaluates all new missions, to make sure they follow the standards and rules laid out in this course. It also means the TAC will personally fly every mission before it gets released.
The TAC of course is not alone: There can be a Command Attache (CA:TAC), and there are many Tactical Surveyors and Tacticians out there to do the hard work. The Tactical Surveyors (TCS) are the ones who beta test the missions, reporting on their experience to the TAC. After that, a Tactician (TCT) is assigned to make any corrections to the battle that are needed before release. This means that when a battle is released, it is flown by at least 5 people (a TCS on each difficulty, a TCT and the TAC or the CA:TAC), so in theory, all bugs and problems should have been found and corrected. However, as the Mission Compendium shows, bugs still make it through. That is why bug reports are important: to catch problems missed during the testing procedure, so that they can be fixed still.
Just because the TAC staff isn't perfect, and bugs sometimes do slip through, the TC database has the option of leaving a bug report. When you're on the download page, there is a link there called "Submit a bug report. I urge everyone to use this option. The TAC (or someone assigned by the TAC), will review the bug reports, and fix battles when needed. The person who submitted the bug report will be informed when the report is deleted.