What determines when a center of reformation will spawn?

[Mindel]

In my campaign I had 3 Protestant centers of reformation appear, and so far 2 Reformed ones. They are all gone now, but the reformed ones did convert a few HRE OPMs before I killed it. Oddly enough, none of these HRE OPMs became a third Reformed center when they converted. Are the rules here different from the Protestant centers?

As I understand it, a third Reformed center could in princple appear, but it hasn't for many years. What determines whether or not it will spawn?

 

[Jespoke]

The Centers of Reformation appear when the state religion changes, which countries are very stubborn against doing sometimes, even with 100% of their provinces converted.

They also don't appear in the provinces directly adjacent to an existing Center.

 

[bestbrian]

I also wonder what factors determine when/where CoR's spwan. Current game is 1.32.1 as Austria. First Protestant CoR appeared in Lucca, which was really convenient as I was at war with Urbino at the time with both of Lucca's allies on my side, so that was an easy smite. Then.....nothing. Eventually, "The Reformation Branches Out" event occurred and Reformed appeared in Lubeck, followed shortly thereafter by another Protestant center in Goslar, which resulted in immediate back to back no CB wars. There are currently four heretic princes in the HRE, and England has gone Anglican, but no further centers have appeared in the last fifteen years. Btw, Council of Trent went full conciliatory even with no one to conciliate with.