This is in Minecraft Bedrock Realms (I assumed the other 'realms' section was for Java realms.)

When I place a sign, type the words, and exit the sign interface, the words actually start erasing themselves to a certain extent. I am unaware of why this has done this, or how long it's been doing this.

Update: It seems to only happen to me, and it only happens when I play on the realm.

Update 2: This bug seems to have been resolved. Thank you!  

I have attached a video of this strange bug.