Determine the which grids may be causing and issue by going to Grids>Repair>Check Geometry in the Exact Surfaces tab.
A message box will display the number of twisted grids.
The twisted grids will highlight in red.
Open the Edit Grids command.
Use the Move/Mark Flow Lines option to zoom into a common area on the grids. Clicking on the grids will straighten the grid line.
Now try the Relax Grids command few more times.
Some grids may require editing or several clicks of relax to get them in shape.
If the Relax Grids algorithms are not able to fix the grids then they will need to be fixed them manually. If this is the case, the only way to fix them would be with the Grids>Edit Grids function. In particular, the Move Grid Points function is the manual approach.