International 9200i won't start

I put a new starter, delco remey 39MT, into my cummins ISX about 3 months, had no issues with it, until today.

Today I started the truck, it started fine, didn't struggle at all, I drove 8 miles and stopped to it to get some breakfast, when I tried to restart it all I get is one click at the starter.

My old starter would do this sometimes, but would always crank on the second try, I ended up replacing this starter as it would slow crank without enough power to start it. But as soon as the new starter went in it started fine.

I spoke to the driver, he said since the new starter has gone in, it did the one click thing once before, but started second time.

I have checked batteries, checked grounds, checked voltage at starter etc

What are the chances the new starter is no good? I doubt it is that, would there be a relay or something somewhere? Any advice would be appreciated.

 

Gave it a few hits with the hammer yesterday, no good, then today I swapped the solenoid on top of the starter and tested both of them, both worked fine, but she still wouldn't turn over. So I was at a witts end, so I gave another few hits with the hammer and now it starts fine.

So a 3 month old starter motor that has something wrong with it.

I am guessing this will happen again and I need to replace it?