Certain characters, when typed on sign, do things they're not supposed to do
When I type a 1, 6, or !, they do things they're not supposed to do.
When I type a 1 or a !, it replaces the character before it.
When I type a 6, the 6 moves to the next line.
(happens in both survival and creative modes.)
MCPE-1955 Text on Signs is weird / Sign letters are erased when you write numbers or exclamation marks