Starter 1975 type 1 beetle

I recently converted my 1975 fuel injected beetle to
a carburetor setup. I finally took it out for a ride
today and all worked well. After shutting it off, it had
a hard time starting (starter would only crank a few
times). After shutting it off again, the starter would
no longer crank at all. I hit the solenoid with a
hammer while trying to start and that did the trick.
This however, only worked once, as it only mad the
starter attempt to turn over after that. My battery is
brand new. I was told it may be a rusty wire
connection but I am looking for other opinions.
Thanks in advance for all the be experts out there.