Segmental analysis is difficult, as expected. There are some diphthongs (or CV sequences) that can only occur in closed syllables - specifically, /iə ia/ before /p m k ŋ/ (/ia/ also before /ʔ/), and /yə/ before /p/. (/iaː/ also occurs, but only in open syllables.)
Length is only contrastive in open syllables. Fricated vowels only occur in Tibetan (?!) loanwords.