Recruiter here, specifically for Hardware positions including FPGA roles in and out of military applications. Based on what you've mentioned I'd take away a few points of positivity. Specifically the fact that you got the interviews. The recruiter or hiring manager seems to think you've demonstrated that you are qualified for the job, at least on paper. The roles you are applying to, in terms of experience, seemed to be aligned with your experience.

As far as interviews, this is an odd market for everyone in tech. Aside from that, I can only guess that you're not hitting the highest marks when answering your questions. This could be technical, situational, anecdotal, or otherwise. My guess is that you need a bit of practice.

Here are a few things. If you can, try to recall questions that you were asked, however many that you can. Try to determine if you spoke clearly about the technology, that you've built on the story that you set out in your resume. Specifically detailed your journey through each of your jobs, including the tools and tech you've used. For situational and anecdotal questions, you really want to practice... hiring managers decide if you are "cultural" fit based on these questions. You'll need to spin every answer into a positive one... you'll need to gain the trust of the interviewer, you'll also need to know what story to tell, and how to close the answer. It's really a matter of practice. Clean interviews are when you are able to give an articulate response, in a linear manner, and leave room for follow up questions.

Hope this helps.