Bugs Messenger

Hello! I really need some help from you guys. For about several months i have something like a bug on my G2 Mini. This problem was on 4.4.2 and now after Lollipop update, still persist. The thing is that everytime when i got a message on Facebook, i tap the ,,message icon,, appears the conversation with that person and when i want to write like 5 words it dissapears the whole conversation. I click again the ,,message icon,, on Facebook and again the same thing:it dissapears. So I need to go to Messenger app and continue my conversation. The exactly same thing happens when i got a message from somebody(not on facebook..just on my phone) and when it appears on screen and i try to write something, again it dissapears, then i need to go again on my message app(standard message app) because i`m not using Hangouts. So i have to go again in my message app and write again the whole thing. This is just getting frustrating and i heard that other people are complaining too. Do you have some kind of solution? Do I need to root my phone? Please help!