After a Guesty sync, locations and groups you linked manually in wp-admin are no longer assigned.
Why this happens. Locations and Groups mirror your Guesty tags. On every run, the sync replaces the site’s assignments with what Guesty has, so links made only in wp-admin are always overwritten. Tags without a prefix are ignored by the location and group sync, which is why setups without prefixed tags reset to zero.
What you can do. To make the links permanent, manage them from Guesty with tag prefixes. Rename or add tags using your account’s prefixes. A tag starting with (l) becomes a Location, and a tag starting with (g) becomes a Group. For example, (l) Domburg creates the location "Domburg" and (g) Tiny House creates the group "Tiny House".
The prefix is stripped during the sync. If the name after the prefix matches a term you already created on the site, the existing page reconnects.