Redirecting to wrong URL - .htaccess

Question

I've been working on a website and have made some changes to my .htaccess file recently. Whenever I went to localhost/company it redirected me correctly, but now whenever I go to localhost/company it redirects me to http://localhost/company.php.php.php.php.php.php.php.php.php.php.php.php.php.php.php.php.php.php.php// with a 404 page error, so obviously that page doesn't exist. It redirects me to the wrong URL.
I am pretty sure the issue comes from my .htaccess file, I've rolled back .htaccess from 3 months ago and this issue still occurs.
Here's my .htaccess:
RewriteEngine On
RewriteRule ^config\.php - [R=404,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/$ $1.php
RewriteRule ^([^/]+)/([^/]+)/$ /$1/$2.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/)$
RewriteRule (.*)$ /$1/ [R=301,L]
ErrorDocument 404 /404.php
RewriteRule ^i(/.*)?/company /company [L,NC]
# disable directory browsing
Options All -Indexes
<FilesMatch "\.(htaccess|htpasswd|ini|phps|fla|psd|log|sh|svn|7z|zip|rar|gz|tar)$">
Order Allow,Deny
Deny from all
</FilesMatch>
I hope you can help me! Thanks!

Answer 1

As mentioned in comments, you will likely get this redirect loop if contact.php does not exist.
RewriteEngine On
RewriteRule ^config\.php - [R=404,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/$ $1.php
RewriteRule ^([^/]+)/([^/]+)/$ /$1/$2.php
Try changing these first few lines to (assuming this .htaccess file is in the document root):
RewriteEngine On
RewriteRule ^config\.php - [R=404,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{DOCUMENT_ROOT}/$1.php -f
RewriteRule ^([^/]+)/$ $1.php [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{DOCUMENT_ROOT}/$1/$2.php -f
RewriteRule ^([^/]+)/([^/]+)/$ /$1/$2.php [L]
This simply checks first that the file would exist, before rewriting. I've also added the L (last) to both these directives - I can't see that any later rules depend on these?