Switch Layer Interpolation Issue in 5.6

[amanandink]

Hey All

Has anyone come across an issue in a switch layer in 5.6. We are using the switch layer to create lip sync and the mouths are in-betweened using interpolation. This works fine except for a small gliche where the switch layer inbetweens are shifting during the inbetweening so that they dont inbetween smoothly, they drift slightly off over the frames of the inbetweening. it jumps on the last inbetween frame to match the next key frame it is inbetweening into. The shifting is only slight but on a close up it is quite noticable.

Has anyone come across this before because it only seems to be on a couple of switch layers we have. does anyone know a work around without having to do a complete redrawing of the mouth shapes.

I hope this all makes sense and if anyone can help I would be very grateful.

thanks
jer