Identifying and filtering duplicates

I have tryed to solve this with DAX on/off for a couple of weeks now with limited success.

I have a large table that each day is filled with subscription data by a script, sometimes the script runs twice, and create duplicate data with different timestamps (DateTime collum).

I wish to identify the duplicates and filter them out in my visuals.

My idea was to first identify if there was a duplicate entry on a given date by counting SubscriptionID, since this should be uniqe each day, adding a True/False collum called "Have Duplicate". Then I would add a True/False collum called "Is Duplicate" determing this using the "Have Duplicate" collum and setting all entries after the first DateTime as True.

I can do a count on SubscriptionID just fine, idetifing if there is duplicates, but as soon as I try to use DateTime to set the "Is Duplicate" it breaks.

I have a DateTable that is related to the Date collum, and I suspect that it is the one breaking it, buy have run out of ideas to solve this.

Best Regards

Ole