This isn’t a direct answer to your question but it’s a similar idea. I speak English and Arabic (native speaker through family and culture) and Arabic is significantly harder for me to speak because a lot of the common sounds in Arabic are what I stutter on, they’re just less prevalent in English. I stutter in both languages, but Arabic can be harder sometimes and there are other times I get through it fine but English is difficult. For me, it was figuring out what aspects of the language were harder and why, then moving from there to figure out what works best to help get through those moments.