The other thing that may have happened is before last winter's freezing temps after the water system was drained, no one drpressed the flush handle and held it down to drain all the water in the valve and line backwards and our the RV water drain spigot. When the water in the valve freezes it expands and stretches the plastic and thus weakens the valve walls or sometimes even cracks or breaks it.
I've seen several that were not drained of our friends alone and the constant spring pressure plus the water pressure together the next season finally blows the weakend valve apart. That's just what they do too and the parts fly all over. Helped 2 of our friends fix theirs this spring. The toilet valve is very often forgotten to be drained as few will think about it.