Events disappearing and unable to re-import
Today I tried to put two new events in Calendar by dragging and dropping .ics files I'd received from the event organiser but the events keep disappearing and I can't re-add them.
When I dropped the first one I was prompted to choose which calendar to put it in and it was correctly added.
I did the same for the second (actually an earlier event) and it was added correctly but I noticed that the first had disappeared. I also noticed that another event added several days ago using a file from the same organiser had also disappeared. I have no idea whether it was there when I entered the first event or not.
I have tried re-adding the event by dragging and dropping the .ics file again. There is a flash of a pop-up for a fraction of a second but nothing after that. By capturing screen video and slowing it down I found that the pop-up is a progress bar with the text "Importing Calendar data..." and the blue of the progress bar already at 100%.
I don't know if the order of the events has any bearing on this but the only event to remain is the earliest one. All the events were in the same calendar.
As far as I can see (and remember) none of the events that I've added manually or imported from .ics files received from other organisations are affected.
Can anyone give me any ideas on troubleshooting?
In case the content of the .ics is having an impact I'm pasting it here. I've used the word "redacted" to show where I've removed details. Anything without an entry is like that in the original file.
BEGIN:VCALENDAR
VERSION:2.0
METHOD:PUBLISH
BEGIN:VEVENT
DTSTART:20200923T180000
DTEND:20200923T183500
LOCATION:
TRANSP: OPAQUE
SEQUENCE:0
UID:
DTSTAMP:20200902T235435
SUMMARY:redacted
DESCRIPTION:redacted
PRIORITY:1
CLASS:PUBLIC
BEGIN:VALARM
TRIGGER:-PT10080M
ACTION:DISPLAY
DESCRIPTION:Reminder
END:VALARM
END:VEVENT
END:VCALENDAR
iMac 27″, macOS 10.14