How to avoid desk rejection of a paper on novel findings?
both sent "desk rejection" one saying "it was out of scope" and other one suggested couple other journals.


I am not going to lie - "out of scope" is a bit the academic version of "it's not you, it's me" in dating. Don't take this feedback as "your paper is ok, this is just not the right place for it". It may easily also just be an editor trying to be polite.

I don't know how common desk rejects are in the biomedical sciences, but in computer science they are rare enough that getting one from a regular journal (as opposed to, say, Nature or Science) is a pretty hefty red flag against a manuscript. Getting multiple desk rejects would mean that I would very critically reflect on the manuscript before trying anything further. Specifically, you say:


  Considering our findings were novel, our written language had no issues, and we tried to do our best with what we had in the lab, what do you think is the issue?


I would encourage you to revisit these assumptions. I don't think that results per se are usually what gets papers desk-rejected, but either a completely inappropriate write-up, submitting to journals where your paper is entirely out of scope, or obvious lack of scientific rigour as expected in the discipline.

I have found it to be a good heuristic to look at a random selection of other recent papers in the journal you want to submit to. Even if your results are novel, your method and paper structure should be similar to some of those. If you can't find any recent paper that resembles yours, it may be out of scope. For empirical work, also take a critical look at sample sizes. If all papers talk about hundreds of participants or survey responses and you have a dozen, talking about the novelty of your results won't get you far - it may still be rejected for lack of rigour. Similarly, if (almost) all other papers are empirical and yours is completely theoretical, or the other way around, look elsewhere.

I am aware that I have not directly answered your actual question: 


  How to avoid desk rejection of a paper on novel findings?


The real feedback I have is - ponder the possibility that, after multiple desk rejects, your problem may not be that your findings are too novel. Get external, unbiased feedback, and find out why the paper appears so problematic to people not close to your work.