There are certain types of rubber/plastic that do this when they degrade, as others have mentioned. I had a small HDD with a rubberized coating on it and rubbing alcohol started to speed it’s degradation and it was a horrific mess. I also had a rubber mallet from a discount tool store that started to stink so bad, and it too was sticky and degrading. And (oh, you thought I was done…) I had some small Rubbermaid totes that I purchased at Walmart over 15 years ago that started to feel greasy and sticky when I touched them. I washed all of them multiple times until I realized the plastic was not cured and was breaking down. At least those did not stink. They only lasted 1 year before that happened.
My lock screen is a B&W photo of a US pay phone. Because you have to pay to use the phone feature.