Access denied while accessing Site Permission under a subsite

User with full control over root site/subsite, gets Access Denied error while trying to access Site permissions under Site Settings of a specific subsite. Same user is able to access Site permissions of all other subsite including the root site.

  1. User has access to the MP gallery/Style Library.
  2. All MPs and CSS are checked-in/published.
  3. User has Full Control on the subsite. Given explicitly.
  4. The site uses the same MP (across entire site collection).

Everything seems to be correct but unable to figure out what can go wrong only with one subsite. Kindly help.