Retention Breakdown (not set) problem

[kgw7401]

Hello, I have a question regarding the use of retention graphs. Currently, I am trying to examine retention by region using the Breakdown feature. However, even though all events have a region property, when I apply the Breakdown, a value of (not set) is generated.

There is (not set) properties in Product Added event

But All Product Added event have region property

In an attempt to resolve this, I tried various methods, and changing the event for which Breakdown is applied from 'Product Added' to 'Product Viewed' resolved the issue.

After conducting various tests, I confirmed that changing the retention event to 'A' resolves the issue, and everything is applied correctly.

Is this a bug in Mixpanel, or am I doing something wrong?