Leftover data - segment filter based on custom fields

Your software
mautic 3.1.1-rc (from github)
php 7.3.22

Your problem
“Leftover” data is showing up in a segment.
I have a custom field called “checks” (boolean field with default to NO).
I have a segment with filter “checks” is eual to NO

Now I have deleted some older contacts, where this field had probably no Default value of NO. Not sure, since I have deleted them. Anyway, in this segment some “Leftovers” keep showing up with no name but the geoIP infos and some tracking infos. So it looks like, not all related data to that contact is removed. Since this is just a test env, all Contacts where created from the same IP (so all geoIP is the same).

Steps I have made:
cleared the cache.
Removed all contacts
Removed the custom field, created new custom field with default value NO,
Removed and recreated the segment with the filter “checks” is equal to NO.

Still those leftover data with IP instead of names is showing up:

If i click on that IP it shows me a the leftover data of a non existing contact:

Connecting up the Github issue for visibility