@”Bernhard “
Sorry for not replying earlier, been a little bit busy.
Theory that your ancestor went from Silesia to Volhynia is not impossible, but I see that as a low probable. The Czechs (some sources saying Czechs and Moravians) were moving to Volhynia mostly in 1868-1880 for better living. At that time Upper Silesia was industrially booming (coal minig, steel production) and life in that area was relatively good so there was not much pressure to leave and look for better place for living.
I would say that Bohemian ancestry is more probable than Silesian.