Hello,

I faced this issue in Odoo 15, and I was investigating for the cause of it, I suspected that it was a customization made which caused it so took a backup and I began to uninstall all custom modules but the error still pop up. I created a new database installing the native modules I am using but the error did not pop up which is very strange, on debugging the code I found that on creating a new company the partner_id is created with a company_id equal 1 not the id of the company which is being created, honestly I do not know why? as the regular behavior to be equal False or equal to the id of the company being created.

 Finally I fixed this issue by overriding the create method of the res.company:

class Company(models.Model):
    _inherit = "res.company"

    @api.model
    def create(self, vals):
        company = super(Company, self).create(vals)
        # Add the following line to avoid user error: Incompatible companies on records.
        company.partner_id.company_id = company.id  # or you can make it = False
        return company

I hope it helps someone.