This isn't a bug with Windy. This isn't really a bug with Meteobridge either. This is just a matter that the Meteobridge Windy upload only supports the default first station (station=0). I would suggest you take this up in the Meteobridge forum. This issue has already been discussed there. It is uncertain if this added feature will be added to the Meteobridge or not. But if enough people ask for the feature it could be added to support additional Windy stations that share an API key. In particular I would recommend posting your concern at this link; https://forum.meteohub.de/viewtopic.php?f=56&t=13565&start=30#p29026
But there is a solution with the Meteobridge that you can do yourself. For the second station (station ID = 1) you could instead of using the Windy upload you instead use the HTTP upload feature in the Meteobridge Services tab. Use the following HTTP code and it will work. Notice that station=1 in this code. The omission of this would assume station=0 which is your primary default station.