Map bosses (and Ridan!) not spawning in mirage

I'm trying to farm the new belt since I'd love to try it, like everyone else this league.

In order to do that I'm farming City Square and clearing everything but the boss and check for the relevant wish. So far I've only encounter the wish three times but for the first two neither any of the map bosses nor Ridan spawned in the mirage. And on the 3rd none of the map bosses did, but after a little while a single Ridan somehow spawned at least.

Sadly I have no video recording of it and I didn't take a screenshot of the area the first two times it happend, but here's one of the 3rd encounter with the single dead Ridan showing:

https://imgur.com/a/aeSQS0i

Edit: It just successfully spawned (and I've seen it work on streams) so it's probably just a rare case. Maybe if the border separates the boss pack it can bug.