Craftsman Lawn Tractor won't start

I bought a 2013 Craftsman Lawn Tractor with a 21 HP Briggs and Stratton motor
It has been good but this fall I started to have trouble starting it.
Replaced the battery,cables,solenoid and starter. Still the same problem. I tried rotating the engine to make sure the motor wasn’t locked uo.
When I rotated the engine until it tighten up(pistons were at the top of the cycle) it started. I’ve had to repeat this each time I want to use the tractor.
Any ideas on what happened or how or what I need to do to fix this I appreciate any insight

What are the symptoms when it doesn’t start?
Does it crank?

Perhaps a faulty compression release?

Pull the valve cover on top of the engine head and make sure the valve tappet bolts are tight. These engines have a problem with them coming loose after a season or two. I have this engine and have to set these valve adjustments every year to make sure the engines starts and runs.

Yes, adjust the valves.

I had a 17 hp briggs powered mower that did the same thing even with a good battery & the valves properly adjusted . Do these engines have a compression release ?

Just googled it & it seems they do . Watched a short u-tube video of how it works . It holds one of the valves slightly open at very low rpm’s .