Why is the base tag ignored when crawled by Googlebot?

Question

Google

Hello.
I found a significant increase in 404 errors in Google Webmasters.
After studying the problem, it turned out that for some reason it began to ignore the base tag :

<base href="http://example.com/" />

<a href="folder1/folder2/page">Link</a>

Instead of prepending the URL from the tag, it tries to access both relative paths, i.e.
The URL of the current page + the path of the link.
http://example.com/folder1/folder1/folder2/page
instead
http://example.com/folder1/folder2/page
In the browser, of course, everything works fine.

Answer 1

It is possible that the matter is in .htaccess RewriteMod