Hi Laura:
I guess you chose the FCA610 for your Rodgers 610 based on "610"
Seriously, I'll take a stab even though I'm not familiar with this unit. My guess is the FCA sampling rate isn't set correctly to match the organ you are loading. Hauptwerk organs are 44Hz or 48Hz the latter being the most popular. Check the driver (you should be using the ASIO driver) and see what sampling rate the Behringer is set at. If you are using the default St. Anne's organ, it is 44Hz but does have a 48Hz variant (St. Anne's for locked 48Hz . .. ).
I'm thinking someone will chime in here soon who actually owns this unit or the expanded FCA1616 model.
Danny B.