@allcoinminer, No haven't gone that far. While trying the different controller cables and power I did feel the heatsink and no matter what I tried the right hand blade did not get warm.
Right hand side with the ethernet port facing you.
Things I've tried- Tried 5 different CX750 power supplies
- Updated to latest firmware (Bitmain support said do this)
- Removed and refitted cables from controller to blades
- Swapped the 2 cables from controller to blades round
- Used combinations of all 4 6 pin power sockets, 2 front, 2 rear and other combinations
Nothing I have tried has worked. Bitmain suggested the firmware update and I've had no other replies from them

Not sure how removing the heatsinks and replacing the paste is going to help?
Any help appreciated

When you swapped the cables from the controller blade, did the miner status change which chain showed to be hashing? Did you also, at that time, confirm that the left hand side continued to warm while the right hand stayed cool?
If so, sounds like a bad blade, and I hope Bitmain would RMA just that blade, and allow you to at least keep the 200GH you do have mining.