If you update the mame core via the online updater your left analog stick will not work properly. I’ve tested it two separate system with different core version. I"m using the Xbox one s via bluetooth.
Mame core 201 works fine. After the moment I update it to the latest version the left analog stick has issues with the up and right directions. I tried to remap them in the mame settings (pressing tab). It looks as though the core is incorrectly interpreting the directions of the left joystick.
I downloaded the latest nightly, and the issue persists.