Nick H,
I'm guessing either you used 'tractor paint' (or rattle cans) without hardener, or the paint was very fresh.
By 'tractor paint' I mean the stuff from the dealer, TSC, etc which is alkyd enamel or acrylic modified enamel.
That is why I won't use anything but automotive paint unless I were just doing a quicky freshening up on a working tractor (which I have yet to do). But if I tear everything apart and remove all the old paint, rust, dirt etc, you can bet I'll spring for the good stuff. No use going to all the work when it can get damaged so easily by something simple like a fuel leak.
I'm not bashing anyone who likes to use rattle cans or tractor paint, I'm just stating why I don't or won't.