I wasn't sure how to tag this, singe it is a question, but it's mostly for fun out of curiosity. We had this experience a couple years ago and I was just thinking about it.
We have this headmate named Rocky, who is an introject of an alien from a book. Back home he spoke a different language, but now he's of course fluent in English. However, there have been rare occasions where he's had trouble communicating due to not having words that previously existed in his old language.
For example, when he first met his sourcemate in our partner system in person a couple of years ago, they were both super happy. The sourcemate apologized for being awkward, and Rocky got a little sad. It turns out that Rocky's previous language didn't see good awkwardness and bad awkwardness as two different versions of the same concept; it saw them as completely distinct emotions and concepts. So when his sourcemate said that he was sorry for acting awkward, Rocky took it as a bad thing. They quickly figured out what was going on and Rocky was relieved, but he still gets a bit annoyed by English's lack of distinct words for things.
Do any other introjects or people with exomemories have moments of frustration when their new language is missing words, or has too many? Or if the grammar or letters are confusing? Our partner system is also a massive linguistics nerd, so we think about how weird languages are a lot.