For a device running , MX Player is widely considered the gold standard for video playback. While the newest versions of the app now require Android 7.0 or higher, legacy versions like 1.9.14 or 1.3.12 are specifically built to support Android 4.1 devices. Core Performance on Android 4.1.2
You downloaded a pirated or modified version. Uninstall it immediately. Get the official free version (1.10.50) which has no license checks. The free version is ad-supported but functions perfectly. mx player for android 4.1.2