Hi LDR,
Narrow chisels and Japanese dovetail chisels can still be problematic. So perhaps a chorus of one.
There are a couple ways to mitigate the issue. One is to carefully tighten both sides down evenly and squarely. Tis the last part of that which affects narrow chisels the most. If the clamp bar sits askew even a little, the pressure exerted on the chisel from a side angle can/will cause the chisel to pivot if not downright move.
Aside from the above, another way to help is to glue a piece of fine sandpaper to the lower roller assembly, across the whole length, where the chisel back makes contact. I have used 180 grit. This works well.
On another trial, I glued a *very* thin piece of neoprene in the same location and I perhaps liked it better. One needs to select a very thin piece, thinner than the former jig had, which was too thick and squishy. That thicker piece only served to allow a certain amount of spring/twist which allowed a narrow chisel to twist anyway.
The above methods have helped many people, but not all. I have then suggested for narrow chisels to purchase an inexpensive side-clamp jig. They have their own bugaboos, but do work for the narrow chisels if they are not too short.
Take care, Mike