I was taught to mainly use a #18 needle on the longarm, although I've used smaller and larger without problems too. Maybe with the titanium needles there's just enough difference to cause the skipped stitches even though you've been sewing with a #16. Here's a link to a question and answer about skipped stitches on the Superior website:
http://www.superiorthreads.com/educa...pped-stitches/. They seem to say needle size could be the problem.
Hope this helps.