Hi Matthes,
This is not the correct place for feedback on Bing Maps. Inside the Bing.com/maps itself there is a feedback tool that collects the exact location and details needed to understand your issue in that area exactly. You can report blurry imagery, poor labeling, bad imagery stiches and more through that method and then it will get to the correct team.
As to BirdsEye specifically, we get that from Vexcel Data. They fly over cities in the summer and collect new data that might not have the same coverage year over year which can lead to some odd features at the edges of these flights. Due to the massive size of these, we can not keep old data but should you need a specific region at a specific time, you could reach out to Vexcel (https://vexceldata.com/) directly to get what you need.
Sincerely, IoTGirl