I wanted to record a video, but I didn't find a nice program to record from Webcam.
Well, I first go into a vast grass, not to the tiny ones and activate a Max Repel. Then, I start the radar. Recently I've been chasing around Bagons, so I go to the shiny patches for the Bagons. Then, I defeat the Bagon and see what the Radar detects on the grass. If it identifies a shiny patch within 4 squares or more, I go to the patch. If not, I just walk 50 steps and try again. For the first times it was good, I had several chain breaking by other Pokémon, but just the normal. Then, yesterday, while I was chaining Bagons, I was defeating the Bagon that would be the 17th on my chain. When the battle was over and I was back in the route, the grass didn't shake, the chain in the Pokétch was gone and the route background music was playing. And that continued to happen with Machops, Swablus, etc, mainly in every chain I tried next, even today. Also, since then, sometimes I am walking in the grass waiting for the Radar to reset and the chain suddenly breaks, like for no reason.
I do not exit the grass area, never go to patches within less than 4 squares and that don't match the original and never go to patches on the corners. Just started to happen with that chain of Bagons. I can't think of it as being bad luck, it would be too much of coincidence, there must be a problem somewhere.