From all issues I have faced in Odoo, this is by fair the most weird one.

I have added the following new field to account.invoice:

early_payment_discount_rate = fields.Float(
   string = 'Discount Rate (%)',
   store = True,
   translate = True,
   help = "Early payment discount applied to total (before taxes).",
)

It works fine but when I try to set a value of 0 or 0.00, Odoo stores 10 in database. Any other value works fine.

I am extremely lost with this issue, any tip to debug or idea that might lead to fix is really welcomed. Thanks a lot.