I keep running into the same problem in trying to book flights/fares that I find on ITA but can't find on UA.com. I force the system to give me the exact same flights and bucket types, yet it ends up being more on UA.com. I called United and they quoted me the ual.com price.

I look on Orbitz and I get the cheaper ITA price. What gives? Am I missing something?

For the intrepid ones in the group. Here is what I trying to buy on Ua.com

UA954 SFO-LHR 2/16 connecting to
LH 6723 (really BD 181) LHR-CDG on 2/17

LH 4123 CDG-FRA on 2/21 connecting to
LH9052 (really UA901) FRA-SFO on 2/21

ITA Fare: $594 all in
UA Fare: more than that by $50 to $150
Bucket type: SLXSNY1E