text: Title: ValueError with 4-hour data, but not 1-hour data 
  Body: Using most up to date versions of everything. As title states, I'm getting a ValueError when I run my code with 4-hour data, but not with 1-hour data. I'm using CSVs. 1-hour data runs perfectly as expected. However, when I export data in exactly the same way, just changing the time interval to 4-hour, I get this warning: "FutureWarning: reindexing with a non-unique Index is deprecated and will raise in a future version" which I don't get when I run the code with the 1-hour data, and then I get this error: "ValueError: cannot reindex on an axis with duplicate labels". The error is originating with df.ta.macd(append=True), however when I comment it out, it just throws the same error with a new line, in my case df.ta.msi(append=True).
  
  Any ideas what's causing the error to occur with 4-hour data, but not 1-hour?