I want to clean up my sales.orders regualary (e-Commerce in odoo 11). 

So I wrote a script, which should delete 200 rows per execution:

dateTime = datetime.datetime.now() - datetime.timedelta(hours = 96)
emptyOffers = env['sale.order'].search(
  [
    ('create_date', '<', dateTime.strftime('%Y-%m-%d %H:%M:%S')),
    ('amount_total', '=', '0')
  ]
)

i = 0;

for emptyOffer in emptyOffers:
    emptyOffer.unlink()
    raise Warning('unlink one') # <= Debug code
    i = i + 1;
    
    if i > 200:
      break;

Everything works fine until "...unlink()". Then the script just runs into timeout => No message, No Exception, Not a single row was deleted

Does anyone know, what i missed?