My weight was incorrectly set for a period of time in zwift and also within zwift power due to a glitch with an auto update from my withings smart scale.
My zwift power race category has me as category B but i can hardly hold 2w/kg.
Will this always remain the case or will it recalculate at some point?
Hi Paul - I’d ask for a the Zwiftpower team for a “Cat reset” based on that argument. I just had a look and can see it was from May till Jan. At least most were group rides so at least you havent been causing too much havoc out there 
Send a note off to zwiftpower@zwift.com - make sure you include your zwiftpower name/id, reason (as you mentioned above). Give them plenty of time - they have a few big curly issues they have been working on so they seem to have a bit of backlog.
The alternative is that Cats are based on best 3 results from past 90 days, so effectively it will take that long to sort itself out.