Languages cause slowdown?

My apps make use of localised strings.

I recently received this email from a customer (who is probably unimpressed by the Google translations)

“Previously, I had the Russian language installed. While using it, the program would noticeably freeze and run more slowly. After I removed the Russian language file through File Explorer, as you suggested, the app started working noticeably faster and more smoothly.”

Obviously I don’t spend any time with my machines in Russian language mode, but should I EXPECT such a performance hit?

Would it be worth compiling separate builds for each language where they are set as the default?

Maybe it can have a small penalty, but it should be a marginal penalty, almost imperceptible after translations loaded, never at the level “freeze”. Deserves investigation. Maybe something is wrong and the translations keep being reloaded all the time? I would prefer investigate and maybe fixing something than building separate apps.