if it's not working, then restarting is the only option. Since you're gonna have to anyways, one recommendation for avoiding that bug would be to never surrender to enemies on your next playthrough. Then, you'll never gain a form before you can swap it out. Play through the entire slime dungeon as a human and get the crystal at the end (farm the areas up to the first chest accessible in human form until you're level 7-8, exiting the dungeon each time so the breakable crates can respawn, then finish the area and you'll be between lvl 10-12. Keep farming to 15 for ease). Afterwards, swap into the slime form and pretty much don't leave it until you've beaten and grinded the Goblin/forest areas to level 25. By then, most of the Slimeform skills will be unlocked, if not all. I'd recommend beating the Faerie Prince at ab lvl 20, then grinding the area with the Beastform for awhile as well (just use the "Smuggler's Hideout" save crystal to teleport to "Tree Village Top" after helping Caspian fix his boat) .You wanna be, at least, lvl 30 before venturing to Dragon Peak to avoid surrendering. Easiest way to put it would be to grind up every form for at least 10 levels each. You won't be able to do much with the dragon form if you do it this way, though, because the game "ends" practically right after you get it. If you want at that point, you can finish the game, or grind the dragon up, and get some chests that weren't accessible before. And never forget that, if you swap MC forms in combat, you get an extra turn to actually use them. It's great when you get skills like "Siphon" in Slimeform, to gain MP for the hero without using items, and Beastform's "Summon Pack" skill does moderate-high damage on all enemies. and use Lyric's songs. The first song has a chance to heal the party on each note, or attack a random enemy, The song "Wildgrowth" does moderate-high damage and inflicts poison on all enemies. "Wildfire" is a bit more useless imo, bc it targets one random enemy with fairly low damage. Just remember, you can't use either of those songs until AFTER "The Forest Song" was played, and they're mainly so OP because they waste no resources.