Hi, I've made a custom module with two models, let's call them "a.py" and "b.py".
I'll write down the important part of the two models for context

A.PY
class A(models.Model):
    _name = 'a'
    codice = fields.Char(string="Codice del corso", required=True)
    costo_a_persona = fields.Monetary(string="Costo (a persona)", required=True)
    currency_id = fields.Many2one("res.currency", string="Valuta", required=True)
    a_b = fields.One2many('b', 'b_a', string="Edizioni del corso erogate:")

B.PY
class B(models.Model):
    _name = 'b'
    number = fields.Text(string="Numero edizione", required=True)
    b_a = fields.Many2one('a', string="Edizione del corso:", required=True)

I would like to give to "b.py" the Monetary and currency_id field (I'll not explain why to simplify, I just need them there too), but if I try to do it in the following way then when I restart Odoo and upgrade the module it would give me back the error:

B.PY
class B(models.Model):
     [...]currency_corso_id = fields.Many2one("res.currency", string="Valuta", required=True)
     costo_corso_a_persona = fields.Monetary(related="b_a.costo_a_persona", string="Costo a persona", store=True)

-> AssertionError: Field b.costo_corso_a_persona with unknown currency_field None