EDIT: I rewrite this completely since I got new findings:
If I build my plugin on Win10, it will not load on Win7 (“Error loading plugin”) on DAW startup. Another DAW will not see it at all.
This only happens with the Release build, Debug loads fine.
Also the version built on Win7 works on both systems.
Is there any way to get more information about what’s happening on the startup (mind that it’s a Release build with almost no output / symbols).