Car grinding after starter replacement. Long story...

What is your question?

I posted this issue before and now there's a new one... A couple weeks ago, I posted on here about a buzzing noise and then it wound up being a bigger issue... it was the starter. I had it replaced and in it's first week, the starter was not working properly and then did the same thing: Everything lit up and no start. So I brought it back to the mechanic since it was under warranty and said it was just connected improperly, honored the warranty and fixed it. Now it's a week later, and the car is making a slight grinding noise after the start up but runs smoothly. This just started today and the fix is only 1 week old after it's last trip. Could it be he just tightened it too much, if such a thing? or is it something else? I think it might be the battery but I'm hoping it's not the starter (again) or something bigger...