If you get an error when completing your order (such as "place order" not working, or some kind of error message), then take screenshots documenting the issue. You can report this in the survey - just answer "NO" to "were you able to place your order?" For reporting the error, you'll receive $5. After you've reported it, you can claim another gig and try a new order with a different Service/restaurant. And yes, error reports count toward your weekly limit.
404 errors DO NOT COUNT - this means you're not logging in correctly. See this FAQ for a 404 error: https://gigwalk.zendesk.com/knowledge/articles/360018078632