Garmin 530 latest 6.2 GPS 4.5 following a course I find that it will tell me "off course" when I get about 50m or so off but when I get back on course I have to ride the course for quite a few minutes before it says "on course". I'm riding trails that I know on a course I know and going off course on purpose to test, sometimes it will tell me up the top of screen the distance back to the course but then after that counts down to zero and I am obviously on course again it doesn't let me know "on course" for ages, about 500m or more on average.
The problem with that is if I get back on course for a couple of hundred meters and then go off course again I get no second warning as it still thinks I'm off course.
My old 520 used to tell me straight away when I was back on course, within about 10 - 20m not 500m or more and a few minutes of riding. In areas where trails are difficult to see this behavior is going to intolerable.
I have tried all the different GPS options and a few of the routing options, nothing has helped so far. Currently I have Popularity Routing OFF, Routing mode Mixed Terrain, Lock to road OFF, Avoidance ALL OFF, Recalculation OFF.