MAME - Can't see the UI in certain systems

[Konamito]

I have a weird problem on my MAME installation. I have mapped one button to show the emulator UI in order to configure parameters.

 

This button works fine in almost all systems but there are some where the UI doesn't show up when pushing the button: MGT Sam Coupé, Sord M5...

 

Here's my samcoupe.cfg file at MAME/cfg:

<?xml version="1.0"?>
<!-- This file is autogenerated; comments and unknown tags will be stripped -->
<mameconfig version="10">
    <system name="samcoupe">
        <image_directories>
            <device instance="printer1" directory="C:\HyperSpin\Emulators\MAME" />
            <device instance="printer2" directory="C:\HyperSpin\Emulators\MAME" />
            <device instance="cassette" directory="C:\HyperSpin\Emulators\MAME" />
            <device instance="floppydisk1" directory="H:\Games\MGT SAM Coupe\" />
            <device instance="floppydisk2" directory="C:\HyperSpin\Emulators\MAME" />
        </image_directories>
    </system>
</mameconfig>

I want to remap the keys for those systems but I can't because I'm not able to enter into the UI.

 

Do you know what is happening?

 

Any idea?