Toilet chronic problem

[mikane]

I have an upstairs toilet that when it leaks it damages the ceilling below, bad.

The last time I reset it, it lasted just over a year then suddenly it leaked. What could be the cause?
Bowl seems to be firm. I dump a Lysol/water solution down the toilet once a week after cleaning bathroom could this be the problem? I use a wax seal with a plastic cone. Its a cast pipe with metal flange.

 

[CT18]

Is the flange cracker which would allow the toilet to rock and break the seal with the wax ring over time.

 

[Geofd]

ct18 is on to something check the flange and wether its secured to the floor...