Faced with flamboyantly unstable responses to control inputs but no warnings of any aircraft system failures, the crew reverted the fly-by-wire aircraft’s controls to direct law (selectable by switch on the pedestal of the ERJ-190), in which the flight control module is removed from the control system and control surfaces respond in proportion to human inputs on the yoke and pedals.
The crew responded by minimising roll inputs wherever possible.
The crew was able to recover sufficient control of the aircraft and divert to Beja, 125 km south-east of Lisbon. Troubleshooting activities by the maintenance service provider, supported by the aircraft manufacturer, lasted 11 days.
Collected and summarized from the source below by Minh Pham https://www.flightsafetyaustralia.com/2019/06/aileron-reversal-led-to-horror-ride/