Honda element starter

My 2003 element starter was sounding like I had a bad battery and eventually stopped completely. The mechanic so far has put 2 different starters in and they both sound like gear teeth grinding but not every time. Maybe 40 or 50 percent. There was no problem with the flywheel previously. The car always starts so far but I am concerned about damaging the flywheel.This is an EX 2wd and I understand there is a difference with the 4wd starter but the replacement is supposed to be the correct one.The mechanic is a neighborhood guy that has a truck and works on the cars at your home. He has been doing this for 32 years and I have used him many times in the past and he has always been good and honest but he is stumped on this one. Something is wrong what can I do?

Installed a new starter from the dealer and it worked fine. Cost twice as much. There were 3 starters the mechanic tried before the new one. They were Bosch. He called Bosch and was told they had a problem but it was supposed to be fixed last January. Apparently not all fixed. The mechanic is a guy who comes to your home with a truck. He has been doing this for 30 years and has done many repairs for me in the past with no problems.
Thanks for the reply.