Thanks to skaman.
The code does a deeper sanity check of the header data when initializing the cart. It avoids having to constantly press buttons to reinit the cart. Carts can still not initialize the MBC properly but that's normal for the WonderSwan. Clean the pins on the cart and check that the cart and adapter are seated properly. If the cart doesn't unlock immediately, then let the sketch run for a bit. For stubborn carts, a power cycle might be necessary.
The sketch fixes a few typos, removes some trailing spaces, and adds another ROM size (used by Benesse Pocket Challenge V2 carts).