I've got a data sheet, which basically contains an amount and a date.

I've created several pivot tables, each on one sheet. I have given names to those tables, such as "tab_days", "tab_weeks", "tab_months", etc. Each table groups the data by the date. The days table groups the amount for every day; the weeks table groups for 7 days; the months groups every month, etc.

I have learned that giving names to pivot tables ensures that their cache and calculations are made independent of every other pivot table in the spreadsheet.

However, one day, I have no idea why, the days table and the weeks tables started sharing the same grouping parameters for the date. That means that if I change the date grouping on the "tab_days" pivot table to every 1 day, the weeks table gets grouped by 1 day. Then I change the "tab_weeks" to group the data every 7 days; back on the "tab_days" data is grouped by 7 days.

How can I clear the link between those two tables? I'd like to have the two tables independent as they were a few weeks ago.