Try to change adl_type parameter, default is 1, try 2.
Put it on "gpu_conf" to get something like that (for intensity, worksize e threads use your stable config, this is only for example):

"gpu_conf" :
[
   { "id" : 0, "intensity" : 50, "worksize" : 4, "threads" : 1, "adl_type": 2},
]


"adl_type" : 1 or 2 , 1 - USE OVERDRIVEN , 2 - USE OVERDRIVE 5. Default is 1 if not set. Option 2 (Overdrive 5) is suitable for older cards