like a programming problem. Dystonia is typically the last thing that DBS affects. Try turning it off for a day if your dad can stand it, and see if that stops the dystonia. the order I attack this problem, is:
1. find out what your dad's settings are. suggest 140 to 180HZ if it is lower.
Ask if his setttings are monopole or dipole. Investigation of Dipole settings mostlikely would be in order. USing dipole settings helps "focus" the stimulation.
2. let the programmer have 10 chances to get it right then look for another.
3. get 2nd opinion of lead placement

there is so much more to tell you, I can't really tell you anymore with out knowing your dads history. A lady in my group went through 4 programmers before she found Sierra Farris in Seattle.

DON"T GIVE UP!!

I have group at Yahoo groups, DBS Surgery. A Google search will take you right to it.
1400 members, many of whom are very knowledgeable about DBS.

Charlie. PD DX'ed in 1990. DBS STN At UCLA in 2002