modification failed when adding lightning calendar item

When trying to add an item to my calendar which is connected to my google calendar, I get "modification_failed" when adding lightning calendar item. Sometimes when snoozing an item. It worked before. I do have the "provider for google calendar" applet installed. Offline mode is off in the settings. I have removed both the applet and the calendar several times. It always synchronizes but I can't add anything. The institutions it gives in the error message doesn't apply to me because I don't want read only access but I want to change either here or on google calendar and have both update. Searching for a solution only reveals tips that are a decade old and don't seem to apply.