i got the same sideway rocking with latest dev build FBW mod but it does seem to fix the issue of default A320 A/P flying parallel (~5nm away) to actual flight plan.
After latest patch, I removed FBW mod and flew the default A320. Out of 5 trials (same flight plans), I encountered twice, crazy right bank that threatens to spin the aircraft down. When it happens, the FD on PFD screen is to the right of the nose…so the A/P try to command the plane to follow the FD. Since it does not happen all the time (rather random), I wonder if this is related to erratic weather (e.g. violent wind?) or ‘disconnection’ between aircraft A/P function and actual flight plan (i.e. Flight Director keep thinking plane should bank right to ‘follow’ flight path endlessly).