Gee, frustrating!
Apparently there were enough changes to CVBasic that the compiler itself needed to be re-compiled. I've built the latest version of WESEB using 0.51, the very latest build of the compiler. If this doesn't work, you'll need to fall back on emulation or another version of the game. Sorry.
Can I ask what hardware and flash cartridge you're using to play this? I'll ask around on SMSPower.org and see if they're having the same problems; they're the only ones I know who would have access to a real, honest-to-goodness SG-1000.