since 3 month h have big pb with " split with ground mesh" fontions ; i found a bug who can perhups explain that .
import a basic item like a cube (
http://supervision2.filnet.fr/froggy/ftp/obj/c1.3ds)
make a first rotate ( no problem)
make another rotate an now you have the problem
ps if you make some operation after/before , move , resize, etc ... you have a different result : objet deformation , missing face , etc ..
and i think if for that my split work one time of 100