Yes, and V4 with old Pentax flashes like AF280T and AF200T in cold is fine, I put them in the snow ( yes under the snow) and they sync great
Only not good when i put the 540fgz and V4 together... it is a common problem and I think GadgetInfinity don't know about it as they are in Asia where always enjoy the warm weather so didn't really able to test it when they are producing them. The main reason I heard from other is that the trigger voltage is so close to what the battery can offer, so when V4 is in the cold, battery can't push enough to make the flash sync fast enough.. don't know if it is true or not.