Zend certified PHP/Magento developer

Magento 2: Desktop and Mobile Themes switched after flushing the cache

I’m using two themes for the Magento 2: Desktop Theme and Mobile Theme. But, I am facing a strange issue. After flushing the cache, If I refresh the site on my desktop, The Desktop version loads correctly. Then, If I open my Mobile and refresh the site, It also loads desktop version! (Not Mobile version).

Same thing happens for opposite process – If I flush the cache, And refresh my site on my mobile first, It loads Mobile version correctly. But When I go to desktop PC, and refresh my site again, It loads Mobile version of my site !.