flash not synced with camera shutter
I just recently purchased a pair of V6s. I shoot with a Pentax K5 and am using a single Pentax AF-540FGZ flash. I can get my flash to fire just fine, but it seems that it is just a slight bit out of sync with the camera. My images consistently come out with the upper portion slightly shadowed, no matter how I aim the flash. I have tried various shutter speeds ranging from 1/30 second to 1/125 second with no change to this shadow. I have made sure the delay is turned off on both V6s. The units are communicating (I can control power on the rx from the tx, and the flash fires when I push the test button on either the camera unit or the flash unit.) Also, without changing any settings on the flash, if I remove the V6s and connect the flash to the camera with a standard sync cord, the flash produces the proper image with no shadowing. I am new to radio triggers in general, but have pored over the Cactus user manual, and have watched (& followed) and online video showing how to set up the V6s. Any help would be appreciated. Thanks!