Hi, I have a suspicion that the issue may be caused by your external SATA convertor devices (multiplier, etc), which may not be properly transmitting the electronic signals between your PC and the drives, thereby causing SyncBack to indefinitely trying to read/get a response, etc.
As I do not have such hardware to test on my end, I can only advise that you try plugging your drive directly to your PC's internal USB ports and run the profile (remember to alter the Source/Destination paths of your profile to suit) again.
If it works via a direct connection, then most likely the issue may be coming from your external devices, which you may need to consult their manufacturers for a solution or an update of firmware (if any), etc.
As I do not have such hardware to test on my end, I can only advise that you try plugging your drive directly to your PC's internal USB ports and run the profile (remember to alter the Source/Destination paths of your profile to suit) again.
If it works via a direct connection, then most likely the issue may be coming from your external devices, which you may need to consult their manufacturers for a solution or an update of firmware (if any), etc.