Miracast no longer working on Windows 10 laptop
The problem might be drivers or BIOS. You may find these at :
The firmware of the TV at the Samsung site, where the latest is apparently version 1510.4 from 2017.09.26. The TV can also update itself if connected to the Internet.
The latest Dell drivers and BIOS for your motherboard at the page of Support for Inspiron 5748 - Drivers & downloads
The latest Intel drivers.
You may also verify in Device Manager the make of the driver of the Miracast device and search for an update.
If all your drivers and firmware are up to date but the problem persists, the problem is then with Windows 10 version 1709, and you will have to wait for Microsoft to fix it. I don't recommend downgrading to an earlier version of Windows, as some have advocated, because of security concerns, and also because Windows will update itself automatically back to version 1709.