Board Thread:Support Requests - Getting Technical/@comment-36189558-20180820083751/@comment-27345308-20180820095947

That's a known bug and you should bother Staff about it through Special:Contact/bug. The more people bothers Staff about a bug, the more they are likely to fix that bug. I'm bothered by that too. It used to be possible to purge the cache using the mobile edit option, but that is gone now due to a lack of use by real editors.

In the meantime, you can open the editor and click on the option for mobile preview. Though that won't work if you're working on pages like your main page, where even editing MMP doesn't automatically update the mobile skin version of the mainpage.