[yitmy]

I suspect you have a posterion deltoid problem not a tricep problem. You have difficulty with the bent over position with your kickbacks. Do you also have difficulty with rear delt flies when in the same position? If you do then you may want to avoid kickbacks till your rear delts get a bit stronger to hold the weight isometrically for you to perform the tricep kick back. So by training your rear/posterior deltoid muscles will the discomfort reduce with other activities. If bent over flies for the posterior delt are too difficult then you may want to perform with cables in the sitting position.

Let us know if this addresses the issues or not.