Somewhat same experience with me. I grew up stuttering in English (native language) and have mostly learned how to navigate talking without it being too noticeable although it does flare up when I'm nervous. But when I started to learn Danish it was like I was 5 years old all over again but the stuttering has reduced quite a bit over time. Of course, it doesn't help that most Danes are fluent in English and will speak English back when they see me hesitate, thinking I don't know the word, rather than me stuttering!