Hi,
If the module is adding any stored compute field to any of the existing model, which has a huge data, this issue will be happening, it is the time taken for computing and storing the value.

To confirm if this is what happening with you, you can check and see the odoo log, it will be something like "Storing value............" in the log.

In order to speed up this, you have to add the field to the db table from the auto_init and set the needed value for the field.

Example:

    def _auto_init(self):

        """

        Create column to stop ORM from computing it himself (too slow)

        """

        if not column_exists(self.env.cr, 'sale_order_line', 'is_service'):

            create_column(self.env.cr, 'sale_order_line', 'is_service', 'bool')

            self.env.cr.execute("""

                UPDATE sale_order_line line

                SET is_service = (pt.type = 'service')

                FROM product_product pp

                LEFT JOIN product_template pt ON pt.id = pp.product_tmpl_id

                WHERE pp.id = line.product_id

            """)

        return super()._auto_init()

Thanks