Craftsman ZTS 7500 issue when trying to start.

Hello everyone, I am new to this forum and I have an issue a Craftsman ZTS 7500, BS V-twin 24hp, 50" cut. First, it has been starting and running great for years. Last year, sometimes when I'd try to start it, The starter kicks in but won't turn the engine... sometimes. IF I hold the key for a few seconds, it might kick, maybe not. If I turn the engine by hand a revolution or so, it might start. If I pull the plugs (new ones), and hit the starter... the engines spins like a top. Put the plugs back in, same thing. Most times when I hit the starter, it will spin the engine about 1/2 to 3/4 of a turn, then stop. Sometimes it will crank and start right up. most times I have to turn the engine by hand to a sweet spot then it might crank. The starter has been swapped with a known good one. Any thoughts??
Thanks.

Craftsman ZTS 7500 issue when trying to start.