Some calendar entries still show after meeting declined, can't be deleted

I frequently receive, via a mailing list, calendar invitations to recurring meetings. I decline most of these meetings. When I use the outlook365.office.com web interface, everything works fine. Meetings that I have declined do not appear in my calendar.

However, some of those declined meetings still appear in my Evolution calendar, and nothing I do will get rid of them. The invitation email is in the trash. If I open the email, I am given the option to decline the meeting (again), but declining it does nothing.

If I right-click on the meeting in the calendar, I am able to open the meeting panel, but the status says "Confirmed", which is false. I can change that to "Cancel", but saving the changes also does nothing. I am not able to close that panel unless I chose to discard all changes.

I can also try deleting meeting, but again, that does nothing. I get an error message that says,

"Failed to delete an event in the calendar “<email address hidden> : Nvidia”

Cannot remove calendar object: The specified object was not found in the store., The process failed to get the correct properties."

I don't know how to further debug this, nor do I know why some meetings on my calendar behave this way. I suspect that somehow Evolution receives and automatically processes the invitation before I have a chance to manually decline it.
---
ProblemType: Bug
ApportVersion: 2.20.11-0ubuntu27.13
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
DistroRelease: Ubuntu 20.04
InstallationDate: Installed on 2020-05-29 (192 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
Package: evolution-ews 3.36.4-0ubuntu1
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 5.4.0-53.59-generic 5.4.65
Tags: focal
Uname: Linux 5.4.0-53-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dialout dip lpadmin lxd plugdev sambashare sudo
_MarkForUpload: True