The Evolution range by Mila has been discontinued but was sold until the early 2010?s. Gearboxes are still available and should be used to replace any faulty units.
Operation: Lift lever or split spindle nightlatch.
Latch reversal: Push in latch, undo screw in side of lock case (adjacent to the latch) to remove the latch. Reverse, reinsert and replace screw.