Remove not used user and remove duplicated cron calls that produce extra calls to the same cron function. The 'company' module has the loop removed here.

__init__.py

@@ -4,7 +4,6 @@
 from trytond.pool import Pool
 from . import activity
 from . import bank
-from . import cron
 from . import employee
 from . import carrier
 from . import party
@@ -12,7 +11,6 @@ from . import party
 
 def register():
     Pool.register(
-        cron.Cron,
         employee.Employee,
         party.PartyCompany,
         party.Party,

cron.py

@@ -1,33 +0,0 @@
-# This file is part of Tryton.  The COPYRIGHT file at the top level of
-# this repository contains the full copyright notices and license terms.
-from trytond.model import ModelView, dualmethod
-from trytond.pool import Pool, PoolMeta
-from trytond.transaction import Transaction
-
-
-class Cron(metaclass=PoolMeta):
-    __name__ = "ir.cron"
-
-    @dualmethod
-    @ModelView.button
-    def run_once(cls, crons):
-        pool = Pool()
-        User = pool.get('res.user')
-        ModelData = pool.get('ir.model.data')
-
-        user = User(ModelData.get_id('party_company', 'user_party_company'))
-
-        for cron in crons:
-            if not cron.companies:
-                super(Cron, cls).run_once([cron])
-            else:
-                # TODO replace with context
-                for company in cron.companies:
-                    User.write([user], {
-                            'company': company.id,
-                            })
-                    with Transaction().set_context(company=company.id):
-                        super(Cron, cls).run_once([cron])
-                User.write([user], {
-                        'company': None,
-                        })