Suspect your problem is partially due to having a fare break and separate segments with inconsistent carryon rules. This is not a common issue and UA had stated it would not allow this combination due to the obvious issues. Don't believe this combination of fare types have been reported by others on a single PNR. Can you provide some detail on how you made this booking? Did you use multi-city? What is the complete routing?

Eventual I would be tempted to get UA to fix the LAX-HNL segment (at no added cost to you but you will need a knowledgeable agent and maybe get a more direct routing). This is an odd ball case.