hey, looked into this issue and found a fix. the source seems to be the variable "store.nia_alert00", which is set to true, and must be set to false for the lvl 31 event to trigger. this variable appears to be new to the recent update. if you're familiar at all with directly editing renpy save files, you can simply change that variable and it should work for you. if you aren't familiar, it's honestly pretty easy, and there are online tools that will allow you to make these kinds of edits.
just upload your save file this site https://arceusx.net/renpy-save-editor/ , change "nia_alert00" to 0 .then download your save and paste your new save file and override