Thought I had gotten a bad batch of batteries because no matter what I did, I couldn’t get an AirTag back online after a replacement.
Turns out, the bitter coating seems to be preventing proper contact in the AirTag. Cleaning the battery off with an alcohol swab solved the problem immediately for me and my AirTag came right back online.
This probably has already prevented the one or other button battery to be swallowed by a toddler.