Yes, just yesterday, after painfully dragging myself back up to 99 ecstatic, I switched devices and found myself at 61 joyous again. I had already wiped out my previous save by the time I had noticed, so there was no going back. So that rules out my first hypothesis about it being an unintended side effect of removing some of the wish tasks--It seems to just occasionally happen when switching devices. Maybe when you play on just one device for a long time, and then switch? Weirdly, at the same time, it seemed like it had bumped me upwards in lifetime visitors. Considering that happiness is ephemeral, and lifetime vistors are marginally less ephemeral, if there's actually a connection, I guess it's not a bad trade, as long as it doesn't happen too often.