Rocking to get it into park is not uncommon. Both my machines with park are that way. Nothing to worry about.
How does your trans oil look? Ever changed it? That would probably be the first thing I would do is dump the transmission oil and look for metal filings on the drain plug and the bottom of the drain pan. Then go on to front and rear differentials if they haven't been changed recently.
If you don't do your own maintenance take it to the dealer or other shop and have the trans oil and differential oils changed. Explain the problem so they know to look for metal. If they don't find anything, great! you have new oil and peace of mind.
Mine: 2018 Sportsman 850SP - 26" Bear Claw HTRs on OEM steel wheels(I really don't like the Aluminum ones)
Polaris Hand warmers, Mirrors.
Hers: 2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. QSC Clutch Kit, Hand Warmers
2001 Magnum 325 MOSE 12" rear wheel conversion. 25" Sedona Coyote tires
2001 Magnum 325 Warn winch and Moose 60" plow
2017 Polaris Ranger 1000XP - Roof and front glass
SOLD 2004 Sportsman 600 Twin