Getting 2 color crappie jigs to weld better

Have issues with baits not sticking together well for like different color tails any advice?

Many on here have way more experience than I....
Have you tried a soldering iron with a thin blade?

I like to shoot my bodies onto tails around 340ish. You can also clean your tails with 92% alcohol especially if they've sat around for awhile as they start to secret oil making the plastic not bond properly.

I'm assuming too much color could cause this too? These are done shooting one color cut tail off putting back into mold then shooting other color

Denatured alcohol or something else?

When I do a two color bait my second color is at about 370 degrees to help bind them together and hold some pressure on that second shot for a ten count or so