Bridging Problems

We have a lead free assembly with a 128-Pin PQFP with 20 mil pitch leads. We have tried stencil aperture reductions, step-down stencils, different thickness stencils, various printer setting changes, placement pressure changes, nozzle changes, moved the placement to a different machine, profile changes and still are having extreme difficulties with bridging. Most of the time, the bridging is not just between two leads but extends accross multiple leads. The paste job is consistent and looks very good as does the placement. Any less paste deposition and we'd have insufficient problems. If you look at a panel prior to reflow, you might see one placement that doesn't look as perfect as the rest and that might be the one that comes out the best - in other words, we don't see much consistency as to where the bridging might occur. We run the exact same product leaded and have very little trouble. Any ideas about what I should try next?

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