@JohnAbbott: Lemmings works!! Hurrah! And it's almost perfect, with the lower screen area having wrong colors: that must be the palette problem you mention. I would fix that, and release 2.41b as Lemmings is probably one of the greatest games to have working in any OS!
@richw: I have no idea what could be wrong, but both Pacmania and Terramex work great here. The Scroll in PACMANIA is, in fact, as smooth as it can be now, so there's nothing strange or notable (besides some keyboard input problems I've with Risc OS, nothing to do with ADFFs).
I would simply use the old 2013 Risc OS image, update the boot partition files to those in BETA12, and copy over the !BOOT contents, then use that to run ADFFS.
We need an updated image for download, but well, that will come with time I hope.