Sorry, I do not know English.Should I will explain briefly.

System Information
WINDOWS 10 64BIT
RYZEN 7 1700X
GTX 780TI

Blender Version
Broken: (2.8 27CCCAECD2)

Short description of error
In Edit Mode "X MIRROR" NOT WORKING

Exact steps for others to reproduce the error
ADD CUBE --> EDIT MODE --> TURN ON "X MIRROR" --> MOVE VERTEX --> VERTEX opposite side NOT MOVE