Sometimes when typing, signs, chat, and command blocks(any where)
when you use < and > to move between letters, it skips complete words
And when you use the backspace button It removes the Whole word
I know it's a bug because there is no setting what so ever, and it can be re-solved by re-logging
Your CTRL key is stuck.
Did you install a non default version of LWJGL ?
Please force a crash by pressing F3 + C for 10 seconds while ingame and attach the crash report here.