Sounds to me as if you are pushing older data onto a chart that already has data for "future" dates. If that is the case then all the data you are pushing through will go to the last bar. It won't overwrite any preexisting data you have.
What you would need to do is go to your Historical Data Manager and remove all historical data for the date you are trying to push data for. Then you would need to open a chart up to that date. Your chart should have no data of that date and then any data you push in from there should be shown on the chart correctly.
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