When water or lava comes in contact with a sign, it breaks the sign

BUG !!!: When water or lava is in contact with a sign, the sign break up. Please fix it because my farms need this system.

My device is Wiko Rainbow Jam.

Steps to duplicate
-Dig down 3 blocks.
-Place sign on the wall of the 2nd block down.
-Place water or lava above the sign (1st block down.)
The water or lava should be held up by the sign but the sign breaks.