Here is a bug regarding recurring invoice template.
If it is set to repeat every 1 month and invoice date is last day of month, it fails to pick next month last day in these conditions:
i.e. if first invoice is generated on 31/10/2018, system will show: Date next gen. 01/12/2018.
It looks like something is related to that November has only 30 days in a month.
Invoice can be issued only after service is delivered, so it is mandatory to have last day of month on invoice.