Residents Parking Permit Renewal Problem - Any Ideas?

Anyone recently tried to renew a residents annual parking permit via the online system?

I went in to do it the other day and it came up with the expected cost but I didn’t have the proof of ownership handy (not sure why I need to do that every year for the same car but maybe someone was gaming the system).

Logged in tonight with the proof of ownership at the ready and it’s decided I have a >3l car registered before 2001 (neither true by a long shot) and trying to charge me a much higher price.

I cannot imagine I will manage to call up to resolve it without ending up getting infuriated. Anyone else had the same issue and was it quick to resolve?