Retro5.net

I recently bought Shining Force 1 & 2 in Japanese. The first game plays 100% fine, but the second one crashes back to the Retron 5 home screen whenever you enter the battle screen. Like when you tell a character to cast a spell, use an item, etc. the game fades out and where it would normally go to a screen showing your character doing whatever action, it just stays black and goes back to the Retron screen. I'm using v2.2

A great number of Genesis/Mega Drive games were broken on firmware v2.2, you likely either need to revert to an older version or upgrade to 2.3 beta

Thanks. If I upgrade to 2.3 beta and have issues, how to I revert?

You would actually need to download an older version and install it on your system.

We have a list of the update versions here: viewforum.php?f=6

Some of the links are no longer valid, but 2.1 has been recently relinked and the thread updated.
I would start with 2.1 and see if that treats you any better.