This is the first time it has happened, but is there a limit to how many of a single pack you can purchase?

I just grinded out 5000 frags so I can buy 5 assassin awakening III packs for the 5* colored shards i need to awaken the shinobi. I purchased 3 of them and then it disappeared from store. if there is a limit, when does it reset? Daily? 3 per day? when was the limit put in place. I am certain I have purchased 5 at a shot before.

Alternatively, you could actually make the 5* colored shards drop... I was ok with them not dropping as long as I can buy what i want with the frags, but now if it is limited then it is a bit of a questionable move.