Strange pop up message

Platform, device version and operating system:
Mobile,Blackview BV5500,Android
Screenshot or image:
No screenshot sorry
**What you were expecting
Got an in game pop up message similar to pet rescue alert except the two green boxes normally reading 'Dismiss/Continue ’ had no txt and I couldn’t select them or do anything else. Can’t remember whole message but part read ‘lots and lots and lots of lovely text’. Froze the game essentially, had to restart. Weird!
How often does this happen? When did it begin happening?
This has only happened once, no-one in my guild has experienced this.