The XML version of the config no longer allows the iptables style verbose rate limit format:

[ firewall name WAN-Local rule 100 limit rate 50/minute ]
'50/minute' is not a valid integer number

The help string for the rate limit is kind of confusing. It’s not entirely obvious to me what value I should use to reproduce 50/minute, as the new version of the config only accepts an integer (that appears to be rendered as RATE/second to iptables internally). If we only support the integer format going forward, we should make some effort to migrate rate limits using the old syntax.