Before you look at what to do with the teams, try to identify what is causing the failures.
Are you conducting retrospectives? Have the team posed any solutions / suggestions about how to improve (scrum emphasizes team and personal responsibility -- the team should be a participant in the solution)
Multiple PO's will almost certainly lead to a more chaotic environment for the team. Part of the elegance of the PO is giving the team one go-to person for final approval on the "What" questions.
But I'm getting ahead of myself -- first, understand the problems really well.
Do you need to merge teams? I don't know, but the 7 +- 2 rule is a pretty good rule of thumb. If you are working on similar things, maybe you need an architecture team. Maybe your team configuration fine, but there is some other hang up in your workflow.
Strongly consider bringing in a good scrum coach. There are a number of training and coaching consultancies out there, and those guys travel the country helping people like us to get implemented.
I've implemented scrum twice now, and I can honestly say that it would not have gone nearly as well as it did if it were not for bringing in training. (You also must have management sponsorship -- for one if my implementations, I was able to get even the CIO to participate in the training -- it was transformational)