One possibility would be to place the field on the level of detail shelf.
Are you able to post a packaged workbook (twbx file) showing the issue?
If you look at the Measure "Received Sentiment", a z-score is calculated using this formula ((Avg([received_sentiment2])-Total(avg([received_sentiment2])))/Total(Stdev([received_sentiment2]))).
However, total() does not use all of the data, but just the data in the row. Is there a way to aggregate all the data, regardless of whether or not it is in the current page?