Cindy,

You can see this on Chrome development tools simulating an iPhone or other small device. Click (tap) on the hamburger toggler. The hamburger is displayed in "hover" mode, and the off canvas menu is displayed. The hamburger remains in "hover" mode. If a link on the offcanvas menu or on the nav bar is tapped, the hamburger icon then goes out of hover mode.

It appears to me that some kind of event must occur to indicate that the offcanvas menu display has completed which would then be a trigger to take the hamburger out of hover mode. This may also be associated with mobile devices trying to emulate mouse hovering over a link or button on a tap device. A quick look on the internet for "sticky hover" shows most attempts to fix are trying to disable hover css on small devices, but I don't think this is the right approach here since the hover is only sticky on the hamburger. But I speculate.

Hope this helps.

Dave