I think your syntax on the advanced routing code is wrong...

UA+ ~YYZ

means "one or more UA flights, not followed by YYZ". So the UA+ could include a pair of UA flights connecting via YYZ. I think what you are requesting is:

UA ~YYZ UA

which would mean "a pair of UA flights, not connecting at YYZ". But this may include codeshares (i.e. AC via BOS). A different way to do this is to express connections positively:

UA EWR,ORD,IAD,IAH,DEN,LAX,SFO UA

so it would list only flights connecting thru UA hubs, which also tends to encourage UA metal. You may get more options changing to "UA+" on either end, but that may reintroduce YYZ.