Hey, manufacturers of things that have plastic parts, what's going on?

I have an old, but well-kept AKG K518LE headphone and suddenly all the matte plastic parts on the headphone are turning into a sticky gooey mess.

I have a Wacom tablet and the Intuos pen had the same issue - the grip area turned also into a sticky gooey mess last year. I was able to rescue the pen by using an automotive plastic conditioner, but this fails on the AKG phone's plastic parts. It reduced the stickyness, but the plastic parts' surface is detoriating and has little dents and is still sticky to the touch. The "wiggle" sticks of the Playstation controllers, they too start to get sticky when not in use for a while.
So, w.t.f.?

There are some online posts describing a similar issue with several plastic parts, be it screwdrivers or sandals, even car dashboards.
Some were able to "fix" this by applying rubbing alcohol, others by treating the surface with baking soda.

But what is going on here in the first place?

Why is the plastic changing, even when not exposed to UV/sun light or in contact with other plastic parts?


With rubbing alcohol - 70% isopropyl - I was able to remove the sticky residue from the AKG phone's parts.

Let's see if this is permanent or just a temporary fix.