Wow is right.

I'm not a chemist, but I am a chemical engineer, so maybe that's close enough.

It could have been a bad batch, like ST says. More likely, the "formula" changed, and it just wasn't tested sufficiently. Maybe that was because the test person was slime and deadlines, career advancement, or profits came before thorough testing. Or maybe the test person was just dumb, and the mistake wasn't caught because the test person's boss was dumb too (or maybe slime). Or maybe everyone at Kiwi did a conscientious and thorough job, but the third-world shoe manufacturers all switched to a new, cheaper kind of glue that dissolves in boot protector. Who knows?

First thing I'd do is check to be 100% sure it's the boot protector that's the problem. If you still have the boots, spray the protector on the glue and confirm that it dissolves. Then contact Kiwi. They might take the high road (remember Johnson & Johnson and the tampered Tylenol), or they might give you the runaround (more likely: send us both pairs of boots at your cost, plus the protector and we'll look at it ...)

I appreciate your bringing this to our attention!