While there is the possibility of some problems, it is probably minimal in this location. As far as I can tell, stainless will release nickle and chromium only if there is actually current passing through it as in a hip prosthesis, knee joint, etc. I had posts in teeth when I zapped and did not have problems with the posts although I have since had the teeth removed. I have not heard of any significant irritation from zapping with stainless steel posts.
This, however, does not mean that you will not experience problems. Use your own judgement.