1997 Will Not Crank

Hi all. I'm the new old lady here so please be patient. Had this issue recently and found that the starter was barely hanging on. My son tightened it up and it did great for a week and now it won't crank again. I've explored some other avenues such as neutral safety switch and solenoid.
It runs great when it runs and it doesn't seem to be "wearing down" between runs. She runs runs great then just decides it won't crank. I would welcome suggestions - and thank you!

*****I JUST REMEMBERED AN IMPORTANT POINT: It is actually a 2013 motor - the previous owner replaced the original.**********