MOZ crawler has been finding a lot of 803 and 804 errors

[Paruyr]

During last 3 weeks MOZ crawler has been finding a lot of 803 and 804 errors. Meanwhile all pages seem to be working fine. What could cause it?

[PatrickDelehanty]

Hi there

First, take a look at Errors in Crawl Reports - there is a lot of great information in there and it's a great resource to help you when you encounter odd or unfamiliar errors.

There are actually quite a few Q+A threads about these exact issues:
How Do I Troubleshoot 804 HTTPS Crawl Error? (Moz)
804 HTTPS (SSL) error (Moz)
How do fix an 803 Error? (Moz)

I would take a look at the following resources because more often than not, this is a mixed protocol configuration:
Configuring HTTPS servers Configuring HTTP and HTTPS

Sometimes it's also because of mixed content. I would also take a look at these mixed content resources:
Fixing “Mixed Content” Errors
Using Protocol Relative Links To Fix Mixed Content Warnings

This should give you a solid place to start! Hope this all helps - good luck!