ZD326 Starter issues??

[Joe Kidd]

Case in point; 5yr old zero turn ZD326(26hp diesel). I'm having cold starting issues. Starter bendix will click but starter will not engage unless I try starting multiple times. I've tried two batteries. My fixed load battery tester(130A) shows "good" with a 15sec test load. Clean connections from the battery post all the way to the starter. I also checked ground chassis connection. When the starter finally engages it'll drag a good bit but generally will start the engine. After I mow for a while restarts are ok. Can a starter exhibit cold weather problems? I even tried two batteries in parallel with the same end result. Any suggestions welcomed. I did notice a crack in the starter "plastic" between the ground and positive posts.