RCS was a dumpster fire for years. Only in the past couple of years has Google stepped up to be the centralized force in making it work as envisioned.

quick edit to say I agree this could’ve been avoided if Apple had made iMessage for Android, but I just wanted to point out the blame is shared by poor implementation across the board.

Some sort of chemical reaction. My best guess would be a drop of CA glue that degraded the material over time.