The very first instance of this chain was game-bu's replacement controversy afaik, cocoa and the other channel that was around back then got the hots from the drama as well and later on the og cocoa choose to walk out as well (she has resurfaced as kannagi tenri recently and is followed by several game-bu's og cast)
Beyond the replacement controversy, I think the main issue they had w/ management was the mistreatment from the staff itself. the replacement issue only happens later after that