I just bought a used Mclane 20" battery powered mower and when
I tried cutting the grass the reel would stop turning. And when I
pulled it back it would start again. Is this because my grass is to
long, about 4 inches long. I had the setting
at 3" on the mower. Or is it the blade that needs sharpening?

I'm using a 20" mclane, 10 blade, battery operated, self propelled.