Question error: expect person received family

I import my data from a gedcom file created in Aldfaer. When I do a check for errors I get with 2 people: expect person, received family.
Those 2 persons are the witnesses of my marriage. So I think that Aldfaer links them to the family and not a person.
I already asked the same question in the Aldfaer forum but I think that I will get a negative answer to modify this.
I (now) think it is a "problem" in Webtrees.
The easiest thing to do is to ignore the error, I know.
Is this something that can be resolved?
edit: in the gedcom file I see this:

1 ASSO @F1661930283@
2 TYPE FAM
2 RELA civil

and that should indicate a relation to the civil marriage.

The GEDCOM code Aldfaer is generating is not valid. The GEDCOM standard 5.5.1 says that the XREF behind ASSO is always related to a person (INDI), not a family (FAM). ASSO links one person to another one.
So you have to add your two witnesses as a person to your tree. Then you can add to your INDI record (and the INDI record of your partner) two ASSO links:
1 ASSO @I1@
2 TYPE witness
1 ASSO @I2@
2 TYPE witness

I found that in the Gedcom-export setting of Aldfaer you can enable GEDCOM 5.5.1 format and then the error is gone.
Thanks for your explanation.