Some overlays with Left+Right positions are intended to be displayed as one information. When both textures are triggered simultaneously, their animations are synchronized.

But when textures are triggered at different times, they may not be synchronized. Especially, their pulse animation is not.

It has been observed with Mage's Fingers of Frost (Cataclysm) which gets stacks one after the other: first stack left, then second stack right. This issue is not specific to mages, neither it is specific to Cataclysm. There may be other effects with the same issue.