Shreddered Mesh on Android

Hi, sorry if someone already had this question. I was not sure what to search for. I made some objects in Blender and imported them via fbx exporter into Unity in the Unity Player everything works fine, but if I export the test game to android, some of the Meshes look shredderes, as if every second triangle is lost or torn to another position (some form a new face between the hands and the legs - looks like rope skipping). That occurs as well on a mesh that has bones as on a mesh without deformation. Both meshes were created with a mirror modifier (which I applied before exporting). So i thought it might have something to do with the modifier. but another mesh created with a modifier looks perfectly well.

Any Ideas?