irmtfan wrote:
I think if you use Rewrite you should always consider strange behaviors.

Found the problem! It was my .htaccess file!

# Turn on rewrites.
RewriteEngine on

# Add trailing slash if path does not contain a period or end with a slash
RewriteCond %{REQUEST_URI} !(\.|/$)
RewriteRule (.*) http://www.domain.com/$1/ [R=301,L]

# Change http://example.com to http://www.example.com (Optional)
RewriteCond %{HTTP_HOST} ^domain.com$
RewriteRule ^/?(.*)$ http://www.domain.com/$1 [R=301,L]

# Only apply to URLs on this domain
RewriteCond %{HTTP_HOST} ^(www.)?domain.com$

# Only apply to URLs that aren't already under folder.
RewriteCond %{REQUEST_URI} !^/Folder/

# Don't apply to URLs that go to existing files or folders.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# Rewrite all those to insert /folder.
RewriteRule ^(.*)$ /Folder/$1

# Also redirect the root folder.
RewriteCond %{HTTP_HOST} ^(www.)?domain.com$
RewriteRule ^(/)?$ Folder/index.php [L]