Odoo Server Error
Traceback (most recent call last):
  File "/home/odoo/src/odoo/13.0/odoo/api.py", line 753, in get
    value = self._data[field][record._ids[0]]
KeyError: <NewId origin=3218458>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/13.0/odoo/fields.py", line 996, in __get__
    value = env.cache.get(record, self)
  File "/home/odoo/src/odoo/13.0/odoo/api.py", line 759, in get
    raise CacheMiss(record, field)
odoo.exceptions.CacheMiss: ('account.move.line(<NewId origin=3218458>,).revenue_monthly', None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 619, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 309, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/home/odoo/src/odoo/13.0/odoo/tools/pycompat.py", line 14, in reraise
    raise value
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 664, in dispatch
    result = self._call_function(**self.params)
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 345, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/home/odoo/src/odoo/13.0/odoo/service/model.py", line 93, in wrapper
    return f(dbname, *args, **kwargs)
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 338, in checked_call
    result = self.endpoint(*a, **kw)
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 910, in __call__
    return self.method(*args, **kw)
  File "/home/odoo/src/odoo/13.0/odoo/http.py", line 510, in response_wrap
    response = f(*args, **kw)
  File "/home/odoo/src/odoo/13.0/addons/web/controllers/main.py", line 1320, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/odoo/src/odoo/13.0/addons/web/controllers/main.py", line 1312, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odoo/src/odoo/13.0/odoo/api.py", line 395, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/home/odoo/src/odoo/13.0/odoo/api.py", line 382, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/odoo/src/odoo/13.0/addons/account/models/account_move.py", line 903, in onchange
    return super(AccountMove, self.with_context(recursive_onchanges=False)).onchange(values, field_name, field_onchange)
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 5993, in onchange
    new_lines.mapped(subname)
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 5184, in mapped
    recs = recs._mapped_func(operator.itemgetter(name))
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 5143, in _mapped_func
    vals = [func(rec) for rec in self]
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 5143, in <listcomp>
    vals = [func(rec) for rec in self]
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 5588, in __getitem__
    return self._fields[key].__get__(self, type(self))
  File "/home/odoo/src/odoo/13.0/odoo/fields.py", line 1020, in __get__
    self.compute_value(recs)
  File "/home/odoo/src/odoo/13.0/odoo/fields.py", line 1105, in compute_value
    records._compute_field_value(self)
  File "/home/odoo/src/odoo/13.0/odoo/models.py", line 3902, in _compute_field_value
    getattr(self, field.compute)()
  File "/home/odoo/src/custom/private/openerp_enterprise/models/openerp_enterprise.py", line 1832, in _compute_revenue_monthly
    months = round((date_stop - date_start).days / (365.2425 / 12))
TypeError: unsupported operand type(s) for -: 'str' and 'str'