I have had something odd happen to my bottle of Plastic Magic glue. It was working fine when at the start of the summer when I last used it.

Yesterday I opened it up to assembled some figures made from injection-moulded polystyrene (Games Workshop minis). I have used this glue for GW models many time and it has always given good results. Yesterday something really strange happened. The glue did not melt the plastic, not even slightly. It just sat in the join looking slightly oily until it evaporated and the pieces fell apart. It has never done that to me before and I am baffled.

Can this type of glue somehow "go off"? Has the crucial solvent evaporated out over the warm summer? Is this glue prone to absorbing moisture from the air and losing its effectiveness? I am totally baffled and I guess I will have to buy a new bottle but I am curious if anyone else has experienced this or knows why it has happened?

I'd have thought more likely some contaminant on the figures?

Test the glue on some other plastics?

The solvent element may have vaporized leaving the carrier liquid.  I don't know this particular glue but I have seen this effect with other solvent based glues.

alternatively were they resin GW figures?