Release Update: Due to a potential issue with the TinyMCE update for the message editor, we have temporarily stopped upgrades to 18.9 and are rolling back TinyMCE to the previous version. Thank you f...
Following on to cjdinger's comment, it would help to know what version of TinyMCE Lithium is currently using to be able to track all the changes going into the 18.9 release.