Don't be surprised if the problem returns quickly. Campy's old dt shifters were notorious for "ghost shifting" as they loosened spontaneously after some use. I had a pair of them on an old Bridgestone and they would begin to shift themselves about every three weeks after I tightened them. I finally replaced them with a set of Sun Tour Power Ratchets and that solved the problem for good.
BTW, in the 60's and 70's many pro teams replaced the Campy shifters on their otherwise all-Campy bikes with Simplex Retrofriction levers just to avoid this problem. You are in good company.