RewriteEngine doesn't work for "profile"

In my website I use RewriteEngine for seo optimization, but I found that if you try use "profile" in rewriting link it doesn't work properly.

Here's an example:

RewriteRule ^profile/([0-9]+)/.+/?$ profile.php?id=$1 [L]

RewriteRule ^profiles/([0-9]+)/.+/?$ profile.php?id=$1 [L]

Link1: http://www.site.com/profile/1/username

Link2: http://www.site.com/profiles/1/username

Both links must loaded to http://www.site.com/profile.php?id=1

But actually only the link2 works properly.

Link1 returns 404 error or some custom pages.

This is a bug caused by CWP because other panels not have this problem and both links works properly.

have you checked the logs and is this maybe related with the mod_security?