Let's get down to business. Facebook has already implemented the reduction of the attribution window, eliminating the 28-day ones. You can see the change at the ad set level, at the bottom, where it will now default to "7-day click or 1-day view":
In general, 2 types of problems are being encountered. Attached is an image of the areas of the Ad Manager that is affected so you know what we are referring to.
The columns of old campaigns are not reflecting correct data.
Source: Facebook bug
Solution: we have seen that activating and deactivating affected campaigns leaving several seconds of margin solves the problem in many cases.
The lower totals column is not adding up the values of the campaign columns.
Source: Facebook cannot show sums of campaign data with different attribution windows (28 days vs 7 days).
Solution: filter and separate campaigns according to their attribution windows so that only campaigns of the same type of attribution window...