Is there a high false-positive rate for co-infection testing?

No, it's the opposite - there's a high false negative rate. Likely due to the lowered immune response due to Lyme and/or Bartonella.

And some LLMD's are now saying that unless you have a very large number of Babesia in your blood at the time of the blood draw, it won't come back positive - whether you have Lyme or not.

There is still so much that is unknown or that we only have a small bit of evidence for with these infections because the infections just haven't been studied long enough or well enough yet. Sometimes, all we have is what some of the more well known, well respected LLMD's believe and what the patients can come up with in their own research.