Copy and Paste creates random null objects from existing geometry i have a really annoying and strange copy &amp; paste bug.

Sometimes when i want to copy &amp; paste an object, blender creates random null objects from my existing geometry, sometimes everything is deleted exept the copied object.
I couldn't reproduce this bug in a new file.

Maybe changed some settings accidentally with a shortcut?

Iam using Blender 2.9 A

Best, Joseph
If you want to duplicate objects in your scene, instead of using Ctrl-C to copy them, consider using Shift-D instead. Admitedly. It's a bit confusing that there are both methods available when they don't seem to completely work the same way. I don't use Ctrl-C for anything except copying poses in Pose Mode. And I have no issues. Interestingly, when I just tried to use Ctrl-C on an object in a scene, as you have done, I got a weird result also: It made an extra copy of my armature object. However, it's an armature that wasn't even part of the object I tried to copy. Very odd.