Ansys Employee

Left handed after a few time steps means the interface isn't working as there are cells being deformed at the boundary.  It may be something you've (not) done, but could also be the newer methods in Fluent as you have several faces making up the interface zones. 

Read   then focus on Section 6.6.4. Once you've diabled the one-to-one pairing delete the non-conformal interfaces and recreate manually.  You may need to reload the mesh as once it's twisted you can't do much with it.