Plasticization strikes again!
Basically, the blast effect bits plastic is soft and bendy because they add a
Plasticizer to it during production.
However some plasticizers used with some plastics can mean that when the plasticized plastic (the blast effects) are held tight to another plastic (the TF), plasticizer compounds can leech across from the blast effect to the TF part. This makes it soft enough that the two get sticky (almost a tiny bit melty seeming) against each other and we see anything from discolouration to bits coming off like this.
It’s the same problem that effects ROTF Bludgeon’s tracks and some other TFs.
Thanks for the heads up! It takes time for plasticizer to leech across so the key is not leaving them plugged together for longer stretches. Eg play is fine but don’t store them connected.