The 4in1 is one of the first things we blame for a problem, and one of the last things to actually cause it. I just experienced a similar problem where I had some tail control, but not what it used to be. I turned my gyro gain up and it didn't help. I changed the tail motor (which I thought was OK), and that was it. I had to turn the gyro gain way down. Now she spins like the cartoon Tasmanian Devil.