I finally worked out what to do, you need to replace the “ORGANIZER” field in each event with one from your existing events that work fine. Right click on an event that works and select show as iCalendar and in the text view that you will be shown you will see a line that starts with “ORGANIZER”, copy that and save for later. Then export the whole calendar that has issues via File>Export and save as an .ICS file. Then open that file, which is just a text file, with a free code text editor like VS Code and use the search and replace function to replace the faulty “ORGANIZER” field(which will look something like ORGANIZER;CN=Family:mailto:***********@group.calendar.google or ORGANIZER;CN=:mailto:*********@gmail.com) with the good one you saved earlier, I did that on 2500 events and it just took a few minutes of fiddling. Once you have done that then save the now corrected *.ICS file and then reimport that back into Emclient into your Google calendar folder, all sorted!