Sounds like you found the right solution. To help claify, there are two incompatible RGB systems widely used now. The plain RGB system uses a 4-pin connector and a 12 VDC power supply line in it. The Addressable RGB (ADDR RGB or ARGB) system uses a 3-pin connector that looks a lot the 4-pin one with one pin missing, and a 5 VDC power supply on one of its lines. The voltage AND the control methods of these two are quite different and you cannot mix the two types in one circuit. IF you have lighting devices of both types, you MUST connect plain RGB devices only to plain RGB controllers, and ADDR RGB devices only to ADDR RGB controllers. That appears to be what you have done to solve your problem.
By the way, the info provided inllustrates how easily these things can get mixed up. You say your controller for the ML240 system does a good job with your ADDR RGB lights. But the ML240L RGB system controller is a PLAIN RGB (4-pin) controller. However, Cooler Master also supplies several ADDR RGB controllers with VERY similar names like ML240P Mirage, and ML240R RGB, etc.