Well, only seeing bubbles in the lines at and around the tops, so that sees ok. When the engine is shut off, they don't seem to move at all, unless you fiddle with the lines themselves, as expected.
So that all looks fine as far as I can tell. I was looking at the line that had popped off, the end that was on the nozzle looked like it had stretched out. When it was warm, it seemed loose on the injector itself, IE you could easily pull it back some. Perhaps it's just getting too hot and slipping off? Are the injectors supposed to get rather warm? I assume that's what the heatsink that sits between the injector and the block would prevent that.