[UPDATE]UDATE

odex25_sales/dev_membership/models/membershib_level.py

@@ -9,7 +9,7 @@ class MembershipLevel(models.Model):
     min = fields.Integer(string='Maximum', required=True)
     max = fields.Integer(string='Maximum', required=True)
     color = fields.Char(string='Membership Card Color')
-    level_no = fields.Char("Number", default=lambda self: self._get_next_levelno(), tracking=True,copy=False)
+    level_no = fields.Char("Number", tracking=True,copy=False)
     sequence = fields.Integer(string="Sequence", help="Define the display order")
     company_id = fields.Many2one('res.company', string='Company', readonly=True,
         default=lambda self: self.env.company)

odex25_sales/dev_membership/models/product_template.py

@@ -14,7 +14,7 @@ from odoo import fields,api, models,_
 class ProductTemplate(models.Model):
     _inherit = "product.template"
 
-    type_no = fields.Char("Number", default=lambda self: self._get_next_projectno(), tracking=True,copy=False)
+    type_no = fields.Char("Number",  tracking=True,copy=False)
     sequence_no = fields.Integer(string="Sequence", help="Define the display order")
     company_id = fields.Many2one('res.company', string='Company', readonly=True,
         default=lambda self: self.env.company)

odex25_sales/dev_membership/models/res_config_settings.py

@@ -59,7 +59,7 @@ class CancellReason(models.Model):
     _description = 'Cancellation Reason'
 
     name = fields.Char(string='Reasone of Cancellation')
-    reasone_no = fields.Char("Number", default=lambda self: self._get_next_reasone_no(), tracking=True,copy=False)
+    reasone_no = fields.Char("Number",tracking=True,copy=False)
     sequence = fields.Integer(string="Sequence", help="Define the display order")
     company_id = fields.Many2one('res.company', string='Company', readonly=True,default=lambda self: self.env.company)