Blender shiny PBR-textures

[NFM]

Hello!
I'm making some custom buildings for my own MSFS scenery.
If viewed in Blender, the pbr-textures are looking perfectly. Meanwhile in MSFS, if you are looking at them at a certain angle, they start to become extremly shiny. I don't know why this is happening.

I use Blender (version 2.93.13), pbr-textures vom ambientcg and the msfs2blend exporter.
Does anyone have an idea what could help?

Thanks!