Fyi, I found a Github dicussion here React bug with Candlestick · Issue #4729 · plotly/plotly.js · GitHub, and after dropping NaN from dataframe using dropna, my problem was solved. Well, almost, because weird candlestick sometime still show up at the noon break (11:30:00 - 13:00:00) of my trading session. I believe that it has something to do with my rangebreaks=[{'bounds' : [11.5, 13], 'pattern' : "hour"}],. Anyway, it’s much better now.
It really seems that NaN or Null values mess up candlestick (but not with OHLC).