SharePoint have something called 'event receiver'. An event is triggered when the user inserts a new record in a list. That event must update a column in the same item. After a few minutes it starts to throw conflict errors while trying to update said column. Doesn't happen with every user. Also I wasn't able to reproduce this behavior in the dev environment.

So now I just recursively call the update method, passing an iterator parameter, repeating the same method until it successfully update the record. Or after 6 failures email someone to see what's going on. Just did it today and published at 7PM. Tomorrow gonna be a long day and I know I deserve it.