[fluffycat]

Turkish is also highly regular and has only one irregular verb. The main problem arises from morphological complexity. Because of these well defined rules that change the rich set of suffixes (>100 different), analysis of a lot of words ends up with many possible parses, it is hard to resolve this ambiguity.

I can't speak Japanese, but if it is also morphologically rich, it should face similar problems.

[szatkus]

In Japanese I think it's pretty straightforward to trace the original word. But there is a fair share of homophones, so if your input is speech-to-text you already have many possibilities without much grammar.