tl;dr: I have removed the Tuesday 19:00 UTC SWAT window from the deployment calendar due to conflicts. Pick one of the other 11 SWAT windows.

The (current) Tuesday 19:00 UTC SWAT window is directly before the 20:00 UTC MediaWiki train window.

The nature of SWAT windows meant that the state of the deployed MW+Extension+Config code was changing while the creation of the new MW train version (eg: 1.29-wmf.8) was happening. This causes delays and confusion.

The simple solution is to not have a normal SWAT window at that time. Other deploys (eg Services) are fine to happen at that time which is why I didn't just extend the MW train window to include that earlier hour.

Luckily, you still have 11 SWAT windows to choose from. :)

Greg