Hello! Unfortunately this is the end-of-life state for a lot of rubberized electronics, the rubber coating just turns back into goop after long enough, especially when heat and sunlight are involved. The best method i've found for removing it without damaging the plastic underneath is a LOT of isopropyl/rubbing alcohol, it'll take a lot of effort but it should get all of that gross stickyness off for good! :) @larrylewand4914