The last four Emperors I?ve tried to catch flee after I tap the screen at the appropriate time. Prior to them, I?d caught a few already and have had no trouble with any other butterflies. Anyone else have this happen?
I think Emperors are a little tricky to catch, they seem to fly away very fast if you don't react soon enough. Sometimes I feel like I tap the screen appropriately as you describe but they still fly away. However, I don't think it's a glitch though. You just need to tap the screen right after the exclamation point pops up.
I am level 58 and have only seen the emperor once way back when I first started playing. I missed it and have never even glimpsed another one. I've completely given up on ever even seeing it again, much less catching one.