I have had a derailment from trailing through an improperly-lined Tortoise-controlled switch. The engine truck of a Lionel hybrid brass 2-8-2 jumped the rail and derailed, as the single axle was not heavy enough to spring the points open. However that's the only derailment I have ever experienced from a continuous movement. On a couple of occasions I have accidentally trailed through an improperly-lined Tortoise switch and then reversed direction before pulling the entire train through the switch. It did what any prototype spring switch would do -- returned to the normal switch point position -- and a derailment resulted.
But I am quite satisfied with the Tortoise motors. The springs require periodic adjustment to make sure the point rail is snug against the stock rail, as do all under the table, spring wire activated switch machines.