Banned Sock Puppet
Well 4Nm = 5.4ft-lbs, so I doubt that was it. I still vote for defective torque wrench. I had a Park Tool torque wrench I was suspicious about. I bought a better torque wrench and sure enough, when comparing, I could feel the Park Tool one was over torquing."About 4NM"? What is "about"?
What brand shoe has a cleat screw torque significantly under 4NM? Because it'd have to be significantly under 4NM in order for you to have pulled the insert out.
Either the shoe was defective, the wrench was defective, or perhaps you converted wrong and used ft-lbs.