Google Crawl Errors and Permalinks

Hi,
The site I’m working on is creating A LOT of google crawl errors. It seems to all be related to the blog and its posts and tags.

it is https://www.domain.com.au/blog/category/post and sometimes https://www.domain.com.au/blog/post

When the website is actually https://www.domain.com.au/post

What causes the google crawl errors and is there a way I can fix them? Also, is the structure of my blog posts incorrect?

Thanks!