Hi Osso,
To get that effect, and also to get the proper colors in sws97 also (to be like PCB), the shadow/highlight palette entry for 0xffe (c355) needs to be either 0x800 or 0x1800. At first I thought this was configured somewhere, the only likely candidate being 3rd word of spriteram (0x0180 gslgr94u, sws97), but j-league contradicts.
Maybe it's just as simple as configuring the shadow offset to 0x800 for nb1?
best regards,
- dink