Problem: Mesh rotates quicker than bone

Problem: Mesh rotates quicker than bone

Hi, I rigged an old model, kinda basic so far, parented by creating empty vertex groups, and started some weightpainting. Now I tried to rotate bones in pose mode a little, to check for deformations, and the mesh rotates with roughly 1.5x speed of the bone itself.

I didnt do any changes to possivly related settings or properties,  and have never seen this before.

Any ideas how that happens? And what to do to eliminate it.

Ty in advance.