Unusual Starter problem

2 days ago van wouldnt start. I have a one month old battery, new terminals.symptoms pointed to replacing starter. Got a re-man starter (#1)and put it in, started great 2 or 3 times. Then no crank. I was able to tap it with hammer and it would start every time I tapped it with hammer. Seemed like a bad starter......so I had parts store warranty it, and I installed #2 re-manufactured starter. It started a couple of times, so I went about my business, errands, it started great another 5 times or so. Then went to drive it last night and no crank again!! This time tapping with hammer didn't work at all. Parts store again warrantied the starter, and We agreed to try a different brand re-man starter. I spent this afternoon out under the van in the rain and put the (#3) starter in. It Cranked!! But only started twice, and now no crank again, and tapping doesn't help. It does make a loud click, 'chunk' sound when I turn key to start. Voltage good to starter, connections clean and tight. Any thoughts, comments, suggestions are welcomed!!