Issue loading arcade games : "No RBF found" when outside of /root

[felleg]

(I am running this on the Taki Udon MiSTer Pi, but I would be very surprised if this made a difference)

# mbc
MBC (Mister Batch Control) Revision 34
Build timestamp: 2023-01-14/16:41:00+00:00
Build commit: 3873450d413c30e6b0339e6b3dbf2373e0e5a74a

I try to run this sample command (the same happens with any arcade game):

mbc load_rom ARCADE '/media/fat/_Arcade/4D Warriors (315-5162).mra'

The game does not load. What happens is it will print a "No RBF found" message on screen if another game is playing. No error is printed on the command line. If on the main MiSTer menu, no message appears. Strangely enough, this only applies to arcade games. I have tested PSX and Saturn games successfully.

I looked inside the MRA to see what RBF was being referenced:

<misterromdescription>
        <name>4D Warriors</name>
        <region></region>
        <homebrew>no</homebrew>
        <bootleg>no</bootleg>
        <version>315-5162</version>
        <alternative></alternative>
        <platform>Sega System 1</platform>
        <series></series>
        <year>1985</year>
        <manufacturer>Sega</manufacturer>
        <category>Shooter - Horizontal</category>

        <setname>4dwarrio</setname>
        <parent>4dwarrio</parent>
        <mameversion>0216</mameversion>
        <rbf>segasys1</rbf>
[...]

Sure enough, I have /media/fat/_Arcade/cores/SEGASYS1_20240602.rbf in my files. To confirm everything is setup correctly, the game loads fine when I launch it from the MiSTer main menu.

[felleg]

I have found a workaround for this issue. If I run mbc from /root, Arcade games launch successfully. I'm not sure what explains this behavior, though. Running from any other location fails.