As originally posted here: Welcome Message Quick Reply options don't always show up on mobile platforms
This is still occurring and still only on iOS devices – users who scroll to read a long prompt message are treated to the quick reply messages vanishing to never return making it very hard to continue interacting with a bot.
We’ve been trying to come up with ways for users to trigger the same menu/set of quick reply options again but nothing has been smooth enough or many enough sense for users to actually do. What we’ve had to rely on is telling users to not scroll. 
Is there an ETA on when this might be fixed? I’ve never seen it occur on Android or any browser version of twitter.