The situation is that, up until .146, they had an older revision of the game (03e-set 2) as the parent 'spacefb' set, and the newest revision (04-u) as a clone set.
They swapped those two versions as of .146, so that the 04-u became the 'spacefb' parent, and downgraded 03e-set 2 to a clone. But what's being tracked on MARP is the 03e-set 2 version, which, since .146, is now 'spacefbe2'.
(This is what they SHOULD do with Mario Bros. already, since they've made an older, super-buggy version with an accidental KS and infinite extra lives as the parent 'mario', and the fixed, revised version as a clone 'marioo'
Eeeediots!
)
Anyway, at the same time that they changed the parent set, they also changed the default settings in such a way that the game is harder.
To make things even more fun, the version that works with newer MAMEs has a different dump than the ones that work with older MAMEs, so you'll also have to find an outdated version of the ROM in order to play it on older MAMEs (though I think RU should have the old one?)
Here is the WIP note from MAMEInfo.dat:
- 0.146u2: Verified dips for Space Firebird and clones [Tafoid].
- 0.145u8: Andy Welburn added clone Space Firebird (rev. 02-a). Dumped mb7051 prom, I8035 audio and gfx2 rom. Changed clones (Nintendo, set 2) to parent 'Space Firebird (rev. 04-u)', (Nintendo, set 1) to clone 'Space Firebird (rev. 03-e set 2)' and (Nintendo, set 3) to 'Space Firebird (rev. 03-e set 1)'. Renamed (spacefb) to (spacefbe2) and (spacefbu) to (spacefb).