Yes, the system will generally show the following bugs:
1. Mixed airline itineraries generally multiples your correct # of bags times the number of airlines in the itinerary for the same direction;
2. Waitlisted with PPs or other instrument will double your baggage allowance since there are two segments for the same flight in your ticket, even though one is waitlisted and not "HK" status
3. Multiple people booked in the same reservation will be the number of bags allowed times the number of pax in the reservation. This can often result in super high baggage numbers being displayed.

Not to mention that after you click on the number of bags allowed you are brought to a different screen that often shows different information and (personally I find) very confusing. The number of bags allowed is displayed in a different area than where you want to 'add bags'. To me the page makes it look like I want to check 2 bags and it should come up as 'free' but instead it's trying to add 2 bags in addition to my free baggage allowance. Maybe I just haven't read the text on the page but I would think United should put right at the top of the page "You are entitled to N free bags for this trip. To add additional baggage and pre-pay the charges please use the form below". Seems simple to me.
-RM