When a fish on a slider runs down to the flasher there is nothing behind the flasher to tangle but the fly. I will unwind a fly to catch a fish. Usually, a slider held tight against a flasher stops the rotation much like a flasher stops rotating when hooked up to a fish. That said, I don't run sliders above meat rigs or when fishing staging kings at harbor mouths as kings are usually concentrated near the bottom and rarely caught on sliders