yum listed firefox.i686 as update package on RHEL6 x86_64 hosts

Issue

• Though firefox.x86_64 was installed in our customer environment, firefox.i686 displayed at the time of yum check-update in 2 servers. Indeed, firefox.x86_64 has been replaced to firefox.i686 in one of those servers. The phenomenon occurs at 2 of 4 servers on similar constitution.
• The phenomenon occurred in Apr 1, it isn't reproduced at present after different handle was done in the respective servers.