This bug has already been reported to the forums 2 months ago but still hasn’t been fixed.
When you press Stop hotkey on your scout, and then switch to the town center, you can accidentally cancel production of villagers or age up technologies.
Already happened to me in a bunch of multiplayer games, several times, especially in dark age, when you are constantly switching between Scout and Town Center, and several times my villager which has been 80% in progress, gets cancelled.
This can be a game losing bug especially in higher than average elos. Once in an arena game i even cancelled a 60% completed Castle Age. It seems to mostly occur in multiplayer, I guess cos of the small delay involved.
I’ve recorded a video on this where i reproduce it in a simple way by spamming scout control group and queuing villagers in the town center. In my hotkey setup, create villager hotkey and Stop hotkey are both set at the letter S. But that isn’t the root cause of this issue. because why do town centers even have the ability to “stop” with the stop hotkey.
In one of these threads, on June 15th, a dev responded that the bug is being tracked, but how is it possible that such a minor bug is unfixed after several patches and 60 days have passed.