Whenever Rikka princess is in the graveyard and I activate it in response to a monster effect, the game instead activates regulus. Others have told me about this bug as well, and I tested it myself and found the same issue
To recreate the bug, all I did was build a regular Rikka sun board. Then when the bot activated their monster effect, I clicked on rikka princess, however instead for whatever reason it had activated Regulus. I had very carefully made sure to choose correctly, yet forever reason it had simply activated Regulus instead
https://duelingnexus.com/replay/969727ea-ff13-4748-b7d6-39839a88e670
In this replay it shows me building the board and ending with princess in grave. When I try to activate princess on the bots turn, regulus activates instead.
I wanted to have tributed strenna, but instead regulus activated, forcing me to tribute lily instead.
I did this on Android, though I’ve had friends who’ve said the same effect occured on windows.