Just another thing....
What I would suggest to combat perceived "reversals of form" is to consider dutch book betting or backing several runners in a race. I would suggest to certainly back your favoured runner but it is probably advisable to "have a saver" on late shorteners as it is common for bookies who are over-committed, to "lay-off" on the tote. Obviously, it is not entirely fool-proof but it is a good bit of insurance to offset some of the these unexpected "form reversals."

Cheers.