The turn restriction you added was not as you wrote in the description - you added left turn only from Crossgate, the wrong road, blocking routing onto both of the A690 routes from that junction.  I assume you are not mapping from personal visits to the locations but perhaps from verbal/written notes from others eg drivers?? If you have not visited the locations you edit, it is absolutely vital that you check all available imagery and all the tags on the ways before making a change, in this case this was clearly and obviously wrong from both the imagery AND the existing tags which you didn't change (or presumably even look at). 
I've removed the false turn restriction and added the actual one - as you described, you cannot turn right from Crossgate Peth to Alexandria Crescent.