Flybacks haven't given me any problems, and I know of several cabinets with this, the DF (completely flat) variant, or the 34" DF model. There is side squishing, but that isn't likely related.
I have known the ACL to be problematic, however. It may be engaging too soon, especially on smallish signals. You can go into service mode (hold up button as you power the device) and adjust the ACL control upwards. Be aware that this may also compromise the ability to prevent phosphor damage if you feed it a huge signal with contrast cranked, so don't go nuts. Be sure to note all original service mode settings, as always, because there's no way to "restore" them.