There are two German words that uppercase to the same: Masse (physical unit, measured in kg usually: mass) and Maße (plural of Maß: measurement). So downcasing MASSE either requires understanding the text or results in a superposition.
These days, we are lucky(?) enough to have ẞ (LATIN CAPITAL LETTER SHARP S) to avoid that particular conundrum ;)
Except that it isn't used widely yet, if at all.
This happens even in English. Downcasing POLISH could give you either an Eastern European nationality or the action you do to shine a shoe, and so needs textual understanding to disambiguate.