That happened to me on a pick 6 I had working about 6 years ago. Hit the first 4 races - all at 5-1 or higher odds (including a 20-1), in the 5th race my horse was scratched at post-time and the betting favorite came up lame at the 1/4 pole. In the 6th race I had the betting favorite at 1-5 and he threw the jockey over the infield fence.
It was a moment where I was counting my money before I earned it - and I haven't been back to the track since.