Nikon d700 hot shoe issues

Hi-

Hopefully someone can help me here. This is my issue: I have a Nikon D700 and just about a month ago  it started acting weird out on shoots. The flash icon was flashing on my camera screen occasionally and wouldn't let me take a picture. I use a sb-29 cord with a Metz flash on a bracket. (Had a SB-900 but the damn thing would overheat and then I miss important shots at events.) I've read in the forums here about some waterguard accessory but since I don't have the weight of the flash on my camera my hotshoe seems to be holding things tight. I did try putting my flash directly on my camera but also had the same issue so that ruled out the cord.  And just yesterday, I had a transmitter on my camera since I was using some strobe lights and I was having some serious overexposure issues. It wasn't consistent either. I would be shooting at ISO 200, 125, f7.1 and for one exposure it would be fine and then the next it was completely blown out. So I would adjust ISO down to ISO Lo.7, 250, f8 and it would still be overexposed. I switched to a different body, a Canon, and had NO issues! Has this happened to anyone else? Do you think it's just the hotshoe that is malfunctioning so it is not getting a proper reading? PLEASE HELP!! Going to bring camera in to a Nikon shop on Monday and just want some feedback before I spend hundreds of dollars. Thank you!