Here was a similar issue, please try to check the dates format one more time
Also, please check the date format that is used to parse data from a data set and to send dates back to the server which is set in date_format config. Default value is %Y-%m-%d %H:%i.
If the issue still exists - please send me the data set (or at least part of it) and I will try to reproduce it to understand te cause.
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