Need help with Sella (Fate, Haruhi Nanao) RVC model on Russian

Hello, sensei! For a couple of months, I've been trying to create my first voice model for personal use (voice packs for home appliances like robot vacuum cleaners) on a loose schedule. I chose Sella (セラ) from Fate. Due to her relatively rare appearance in anime, I only managed to collect 7 minutes and 30 seconds of clean recordings. I initially trained her from scratch, but since the dataset was Japanese, she handled Japanese lines well (like Leysritt's). However, when switching to my language, Russian, she lost the pronunciation of the Russian "R"s and began to sound unnatural.