Users have tried force closing the app, as well as deleting and reinstalling it, but nothing has yet fixed it. Facebook confirmed that it is looking into the bug, "but for now there's no word from the company on what is causing it and how it plans to fix it."
DearFacebook, pleaseFix messenger so ICan typeMoreThanA couple wordsThanks - Adam Colgan 🏳?🌈 (@nerdenator) January 18, 2018
One user reported that the bug caused their iPhone 6s Plus to crash, and another theorized that the source of the problem might be with the app's autocorrect function.
Earlier this week, Facebook vice president of messaging products, David Marcus, admitted that Messenger's mobile app has become "too cluttered." In response to this, the company will invest in "massively simplifying and streamlining" Messenger in 2018.
Article Link: Facebook Messenger Bug Preventing Some iPhone Users From Being Able to Type Messages